ScriptingCore.cpp ccdictionary_to_jsval() BUG

In ccdictionary_to_jsval(), if ‘dict’ is NULL, the function will crash.
I found this during testing TMX tile map’s propertiesForGID(). When a tile map’s GID doesn’t have any property, it crashes.

this in bindings/ScriptingCore.cpp causes the crash:
" CCDICT_FOREACH(dict, pElement)"

Thanks, issue #1644 was created.