NPE in issueworklogged.vm if work description is empty

Logging work without a description triggers a NullPointerException during email notification (templates/email/text/issueworklogged.vm).
It looks like the context variable $changelog is null:

2006-03-30 09:57:11,738 ERROR [velocity] Method indentToChangelog threw exception for reference $velocityhelper in template templates/email/text/issueworklogged.vm at [1,1]
2006-03-30 09:57:12,105 ERROR [com.atlassian.velocity.DefaultVelocityManager] MethodInvocationException occurred getting message body from Velocity: java.lang.NullPointerException
java.lang.NullPointerException
at com.atlassian.jira.util.JiraVelocityHelper.indentToChangelog(JiraVelocityHelper.java:242)
at sun.reflect.GeneratedMethodAccessor1187.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:267)
at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:197)
at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:175)
at org.apache.velocity.runtime.parser.node.ASTReference.render(ASTReference.java:220)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:230)
at org.apache.velocity.runtime.directive.VelocimacroProxy.render(VelocimacroProxy.java:172)
at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:114)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:230)
at org.apache.velocity.Template.merge(Template.java:256)
at org.apache.velocity.app.VelocityEngine.mergeTemplate(VelocityEngine.java:450)
at com.atlassian.velocity.DefaultVelocityManager.getEncodedBody(DefaultVelocityManager.java:76)
at com.atlassian.velocity.DefaultVelocityManager.getEncodedBody(DefaultVelocityManager.java:60)
at com.atlassian.jira.mail.MailingListCompiler.sendLists(MailingListCompiler.java:155)
at com.atlassian.jira.mail.MailingListCompiler.sendLists(MailingListCompiler.java:100)
at com.atlassian.jira.mail.IssueMailQueueItem.send(IssueMailQueueItem.java:114)
at com.atlassian.mail.queue.MailQueueImpl.sendBuffer(MailQueueImpl.java:68)
at com.atlassian.jira.service.services.mail.MailQueueService.run(MailQueueService.java:23)
at com.atlassian.jira.service.JiraServiceContainer.run(JiraServiceContainer.java:59)
at com.atlassian.jira.service.ServiceRunner.execute(ServiceRunner.java:50)
at org.quartz.core.JobRunShell.run(JobRunShell.java:191)
at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:516)