Fixed filtering bug, use correct expression

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@11789 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
bugfix

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@11790 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
bugfix

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@11791 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c