Merged revision 1597532 from tomcat/trunk:
Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=56561
Fixed NoSuchElementException when an attribute has empty string as value.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc6.0.x/trunk@1597837 13f79535-47bb-0310-9956-ffa450edef68