as reported here https://issues.apache.org/bugzilla/show_bug.cgi?id=46084 it seems to be a bug of Tomcat.
Moreover you can see this: https://issues.apache.org/bugzilla/show_bug.cgi?id=42565
If you try to search this error in Internet you can see other similar cases and the possible solution is:
Replace EL exepressions containing "empty(" with "empty (", and "not(" with "not (" as EL expression requires (add whitespace). In this case you should edit the Style project templates in order to replace the codes.
The easy way is to deploy the webapp on a Tomcat that includes the fix.
Can you tell us the version of Tomcat in use in which your webapp is deployed?