Fix the build after after r169789 on platforms that build with -Wunused-const-variable

* bindings/scripts/CodeGeneratorJS.pm:
(GenerateHashTable): Don't create the value array if it'll never be used.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@169800 268f45cc-cd09-0410-ab3c-d52691b4dbfc