Steps to reproduce:

1. Create a page with a gallery macro:

   {gallery}

2. Do not attach any images to the page
3. Export the page to PDF or HTML via Space Admin->Advanced->Export Space. Please note that the problem does not exist if you export the page to PDF through the "Tools->Export to PDF" menu

The HTML or PDF page will contain an error message:

Error trying to draw image gallery org.apache.velocity.exception.MethodInvocationException: Invocation of method 'requireResource' in class $Proxy48 threw exception java.lang.NullPointerException @ /com/atlassian/confluence/plugins/macros/advanced/gallery-default.vm[1,25]

In Confluence version prior to 2.9, a nice message is presented to the user instead:

There are no images attached to this page

The following stack trace recorded in the log during the export:

2009-02-04 18:25:15,531 ERROR [Export Space task] [plugins.macros.advanced.GalleryMacro] execute Error while trying to draw the image gallery
– url: /confluence/spaces/doexportspace.action | userName: admin | referer: http://localhost:8100/confluence/spaces/exportspace.action?key=~admin | action: doexportspace
org.apache.velocity.exception.MethodInvocationException: Invocation of method 'requireResource' in class $Proxy48 threw exception java.lang.NullPointerException @ /com/atlassian/confluence/plugins/macros/advanced/gallery-default.vm[1,25]
at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:286)
at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:203)
at org.apache.velocity.runtime.parser.node.ASTReference.render(ASTReference.java:294)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:318)
at org.apache.velocity.runtime.directive.VelocimacroProxy.render(VelocimacroProxy.java:194)
at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:170)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:318)
at org.apache.velocity.Template.merge(Template.java:254)
at com.atlassian.confluence.util.velocity.VelocityUtils.getRenderedTemplateWithoutSwallowingErrors(VelocityUtils.java:58)
at com.atlassian.confluence.plugins.macros.advanced.GalleryMacro.execute(GalleryMacro.java:100)
at com.atlassian.renderer.v2.macro.ResourceAwareMacroDecorator.execute(ResourceAwareMacroDecorator.java:45)
at com.atlassian.renderer.v2.components.MacroRendererComponent.executeMacro(MacroRendererComponent.java:196)
at com.atlassian.renderer.v2.components.MacroRendererComponent.processMacro(MacroRendererComponent.java:154)
at com.atlassian.renderer.v2.components.MacroRendererComponent.makeMacro(MacroRendererComponent.java:58)
at com.atlassian.renderer.v2.components.WikiContentRendererHandler.handleMacro(WikiContentRendererHandler.java:18)
at com.atlassian.renderer.v2.WikiMarkupParser.makeMacro(WikiMarkupParser.java:126)
at com.atlassian.renderer.v2.WikiMarkupParser.makeMacro(WikiMarkupParser.java:114)
at com.atlassian.renderer.v2.WikiMarkupParser.handlePotentialMacro(WikiMarkupParser.java:99)
at com.atlassian.renderer.v2.WikiMarkupParser.parse(WikiMarkupParser.java:60)
at com.atlassian.renderer.v2.components.MacroRendererComponent.render(MacroRendererComponent.java:43)
at com.atlassian.renderer.v2.V2Renderer.render(V2Renderer.java:53)
at com.atlassian.renderer.v2.plugin.PluggableV2Renderer.render(PluggableV2Renderer.java:30)
at com.atlassian.renderer.v2.V2RendererFacade.convertWikiToXHtml(V2RendererFacade.java:57)
at sun.reflect.GeneratedMethodAccessor329.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:304)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
at com.atlassian.spring.interceptors.SpringProfilingInterceptor.invoke(SpringProfilingInterceptor.java:20)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
at $Proxy55.convertWikiToXHtml(Unknown Source)
at com.atlassian.confluence.importexport.impl.WikiExporter.exportWikiToXHtml(WikiExporter.java:124)
at com.atlassian.confluence.importexport.impl.WikiExporter.exportWikiToXHtml(WikiExporter.java:82)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:295)
at com.atlassian.confluence.velocity.introspection.AnnotationBoxingMethod.invoke(AnnotationBoxingMethod.java:28)
at com.atlassian.confluence.velocity.introspection.UnboxingMethod.invoke(UnboxingMethod.java:29)
at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:245)
at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:203)
at org.apache.velocity.runtime.parser.node.ASTReference.render(ASTReference.java:294)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:318)
at org.apache.velocity.Template.merge(Template.java:254)
at com.atlassian.confluence.util.TemplateSupport.processTemplate(TemplateSupport.java:71)
at com.atlassian.confluence.importexport.impl.HtmlExporter.doExportEntity(HtmlExporter.java:179)
at com.atlassian.confluence.importexport.impl.HtmlExporter.exportPage(HtmlExporter.java:87)
at com.atlassian.confluence.importexport.impl.HtmlExporter.exportSpace(HtmlExporter.java:99)
at com.atlassian.confluence.importexport.impl.AbstractRendererExporterImpl.doExport(AbstractRendererExporterImpl.java:86)
at com.atlassian.confluence.importexport.impl.HtmlExporter.doExport(HtmlExporter.java:31)
at com.atlassian.confluence.importexport.DefaultImportExportManager.exportAs(DefaultImportExportManager.java:112)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:304)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
at $Proxy68.exportAs(Unknown Source)
at com.atlassian.confluence.importexport.actions.ExportSpaceLongRunningTask$1.doInTransactionWithoutResult(ExportSpaceLongRunningTask.java:88)
at org.springframework.transaction.support.TransactionCallbackWithoutResult.doInTransaction(TransactionCallbackWithoutResult.java:33)
at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:127)
at com.atlassian.confluence.importexport.actions.ExportSpaceLongRunningTask.runInternal(ExportSpaceLongRunningTask.java:59)
at com.atlassian.confluence.util.longrunning.ConfluenceAbstractLongRunningTask.run(ConfluenceAbstractLongRunningTask.java:21)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.NullPointerException
at com.atlassian.plugin.webresource.WebResourceManagerImpl.getIncludeMode(WebResourceManagerImpl.java:261)
at com.atlassian.plugin.webresource.WebResourceManagerImpl.requireResource(WebResourceManagerImpl.java:58)
at com.atlassian.confluence.plugin.webresource.DefaultConfluenceWebResourceManager.requireResource(DefaultConfluenceWebResourceManager.java:49)
at sun.reflect.GeneratedMethodAccessor233.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:304)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
at $Proxy48.requireResource(Unknown Source)
at sun.reflect.GeneratedMethodAccessor232.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:295)
at com.atlassian.confluence.velocity.introspection.UnboxingMethod.invoke(UnboxingMethod.java:29)
at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:245)
... 72 more