Cannot delete project if a portlet (Project Stats) is associated with it.

1. Create a portlet (Project Stats) associated with a specific project.
2. Delete the project.

JIRA displays the following error:

Exception removing project: Error in action: com.atlassian.jira.action.project.ProjectDelete@412f4b, result: null

and the following stacktrace is thrown:

Caused by: com.opensymphony.user.EntityNotFoundException: No user null found
at com.opensymphony.user.UserManager.getEntity(UserManager.java:302)
at com.opensymphony.user.UserManager.getUser(UserManager.java:193)
at com.atlassian.jira.action.project.ProjectDelete.removeProjectPortlets(ProjectDelete.java:169)
at com.atlassian.jira.action.project.ProjectDelete.doExecute(ProjectDelete.java:113)
at webwork.action.ActionSupport.execute(ActionSupport.java:151)
at com.atlassian.jira.action.JiraActionSupport.execute(JiraActionSupport.java:46)
at com.atlassian.jira.action.JiraNonWebActionSupport.execute(JiraNonWebActionSupport.java:27)
at webwork.dispatcher.GenericDispatcher.executeAction(GenericDispatcher.java:131)
at com.atlassian.core.action.DefaultActionDispatcher.execute(DefaultActionDispatcher.java:34)
at com.atlassian.jira.web.action.project.DeleteProject.doExecute(DeleteProject.java:31)
... 31 more