Crash when modifying dashboard elements

Profile > Dashboard Configuration

When trying to delete / move some dashboard elements, an exception occurs (see log below). Eventually, dashboard settings for other users are altered.

This error happened for some users systematically, and never for others.
I could reproduce it on Atlassian bugtrack with my account

java.lang.NullPointerException
at com.atlassian.jira.portal.PortalPageConfigurationImpl.deletePortletConfig(PortalPageConfigurationImpl.java:149)
at com.atlassian.jira.web.action.user.ConfigurePortal.doDelete(ConfigurePortal.java:262)
at com.atlassian.jira.web.action.user.ConfigurePortal.doExecute(ConfigurePortal.java:191)
at webwork.action.ActionSupport.execute(ActionSupport.java:114)
at webwork.dispatcher.GenericDispatcher.executeAction(GenericDispatcher.java:113)
at webwork.dispatcher.ServletDispatcher.service(ServletDispatcher.java:161)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:336)
at com.evermind._it.doFilter(.:59)
at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:128)
at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:60)
at com.atlassian.jira.web.filters.SitemeshExcludePathFilter.doFilter(SitemeshExcludePathFilter.java:35)
at com.evermind._ir.doFilter(.:16)
at com.atlassian.core.security.SecurityFilter.doFilter(SecurityFilter.java:170)
at com.evermind._ir.doFilter(.:20)
at com.atlassian.core.security.LoginFilter.doFilter(LoginFilter.java:173)
at com.evermind._ir.doFilter(.:20)
at com.atlassian.util.filters.ProfilingFilter.doFilter(Unknown Source)
at com.evermind._ir.doFilter(.:20)
at com.atlassian.jira.web.filters.EncodingFilter.doFilter(EncodingFilter.java:53)
at com.evermind._ir.doFilter(.:20)
at com.orionserver.http.patch.PathInvalidationFilter.doFilter(PathInvalidationFilter.java:150)
at com.evermind._efb._plc(.:380)
at com.evermind._efb._adc(.:174)
at com.evermind._cs._yqb(.:614)
at com.evermind._cs._yrb(.:189)
at com.evermind._bx.run(.:62)