Projects portlet broken

In JIRA Enterprise, it's possible for the projects portlet to break:

Error rendering /portlets/dashboard/projects.jsp: null.
Removing and recreating this portlet may solve the problem.

And in the logs, an exception:

Exception rendering portlet /portlets/dashboard/projects.jsp
org.apache.jasper.JasperException
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.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684)
at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:575)
at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:498)
at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:822)
at org.apache.jsp.dashboard_jsp._jspService(dashboard_jsp.java:570)
...