Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=54242
Fix NPE in tagPlugins:ForEach when iteration is null. JSTL spec says it should be treated like an empty iteration.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1427846 13f79535-47bb-0310-9956-ffa450edef68
Test case for https://issues.apache.org/bugzilla/show_bug.cgi?id=54242

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1427848 13f79535-47bb-0310-9956-ffa450edef68