If a user has a filter (saved search) that searches a project which has subsequently been deleted, the 'filters' page (top-right link in the dashboard) breaks with this error:

org.apache.jasper.JasperException: The entity passed must not be null
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:254)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:295)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
....
root cause

java.lang.IllegalArgumentException: The entity passed must not be null
at com.atlassian.jira.security.AbstractPermissionManager.hasPermission(AbstractPermissionManager.java:101)
at org.apache.jsp.savedfilters_jsp._jspService(savedfilters_jsp.java:80)