Anonymous comment in a ticket causes error rendering ActivityModule in Issue Navigator

Summary

When enabling Service Desk for a normal project, there will be an error viewing the issue if that particular issue has a comment made by Anonymous users

Steps to reproduce

1. Create a normal project
2. Give Group (Anyone) permission to browse project and comment on issue
3. Create an issue in the project
4. Have an anonymous user (not logged in) comment on that issue
5. Enable Service Desk for the project
6. View that particular issue in the Issue Navigator

Expected Results

1. Everything works normally
2. Able to view the issue without any errors

Actual Results

1. When viewing the issue in the Issue Navigator, there will be the following error
   
2. The following stacktrace is found in the logs:

   2015-02-27 08:48:25,556 http-bio-8080-exec-18 WARN admin 528x266768x1 5hjovl xxx.xxx.xxx.xxx,127.0.0.1 /browse/KEY1556 [com.atlassian.ozymandias.SafePluginPointAccess] Unable to run plugin code because of 'java.lang.NullPointerException - null'.
   2015-02-27 08:48:25,557 http-bio-8080-exec-18 ERROR admin 528x266768x1 5hjovl /browse/KEY-1556 [jira.web.component.ModuleWebComponentImpl] An exception occured while rendering the web panel: com.atlassian.jira.jira-view-issue-plugin:activitymodule (null)
   com.atlassian.templaterenderer.RenderingException: org.apache.velocity.exception.MethodInvocationException: Invocation of method 'getHtml' in  class com.atlassian.jira.issue.tabpanels.CommentAction threw exception java.lang.NullPointerException at viewissue/activityblock.vm[line 52, column 27]
   ...
   Caused by: org.apache.velocity.exception.MethodInvocationException: Invocation of method 'getHtml' in  class com.atlassian.jira.issue.tabpanels.CommentAction threw exception java.lang.NullPointerException at viewissue/activityblock.vm[line 52, column 27]
   	at org.apache.velocity.runtime.parser.node.ASTIdentifier.execute(ASTIdentifier.java:223)
   	at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:262)
   	at org.apache.velocity.runtime.parser.node.ASTReference.render(ASTReference.java:342)
   	at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72)
   	at org.apache.velocity.runtime.directive.Foreach.performIteration(Foreach.java:393)
   	at org.apache.velocity.runtime.directive.Foreach.render(Foreach.java:316)
   	at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:175)
   	at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72)
   	at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:87)
   	at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72)
   	at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:87)
   	at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:336)
   	at org.apache.velocity.Template.merge(Template.java:328)
   	at org.apache.velocity.Template.merge(Template.java:235)
   	at com.atlassian.templaterenderer.velocity.one.six.internal.VelocityTemplateRendererImpl.render(VelocityTemplateRendererImpl.java:100)
   	... 338 more
   Caused by: java.lang.NullPointerException
   	at com.atlassian.fugue.Option$3.apply(Option.java:400)
   	at com.atlassian.fugue.Option$3.apply(Option.java:398)
   	at com.google.common.collect.Iterators$7.computeNext(Iterators.java:649)
   	at com.google.common.collect.AbstractIterator.tryToComputeNext(AbstractIterator.java:143)
   	at com.google.common.collect.AbstractIterator.hasNext(AbstractIterator.java:138)
   	at com.google.common.collect.Iterators.getNext(Iterators.java:890)
   	at com.google.common.collect.Iterables.getFirst(Iterables.java:781)
   	at com.atlassian.jira.issue.fields.renderer.comment.DefaultCommentFieldRenderer.renderCommentFields(DefaultCommentFieldRenderer.java:106)
   	at com.atlassian.jira.issue.fields.renderer.comment.DefaultCommentFieldRenderer.getIssuePageViewHtml(DefaultCommentFieldRenderer.java:61)
   	at com.atlassian.jira.issue.tabpanels.CommentAction.getHtml(CommentAction.java:132)
   	at sun.reflect.GeneratedMethodAccessor1234.invoke(Unknown Source)
   	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   	at java.lang.reflect.Method.invoke(Method.java:606)
   	at org.apache.velocity.runtime.parser.node.PropertyExecutor.execute(PropertyExecutor.java:142)
   	at org.apache.velocity.util.introspection.UberspectImpl$VelGetterImpl.invoke(UberspectImpl.java:525)
   	at com.atlassian.velocity.htmlsafe.introspection.AnnotationBoxingPropertyGet.invoke(AnnotationBoxingPropertyGet.java:26)
   	at org.apache.velocity.runtime.parser.node.ASTIdentifier.execute(ASTIdentifier.java:198)
   

Notes

Tested with JIRA 6.3.15 and Service Desk 2.2