Better handle property-not-found: Avoid NPE

git-svn-id: http://scmcit.gva.es/svn/gvnix/trunk/code@2660 69435866-3869-0410-973d-9f951a852354
Refs #13732 - Adding Filter Assistant
Refs #13726 - Solving Errors on Inline Editing

git-svn-id: http://scmcit.gva.es/svn/gvnix/trunk/code@2661 69435866-3869-0410-973d-9f951a852354