Merged revision 1517536 from tomcat/trunk:
javax.el.BeanELResolver:
- getFeatureDescriptors, getCommonPropertyType do not throw NPE when the supplied context is null.
- unit test is added

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc7.0.x/trunk@1517586 13f79535-47bb-0310-9956-ffa450edef68