When javascript code is called on recently destroyed context, QmlContextWrapper::callingContext function returns null pointer.

There's no sanity check in __qmljs_get_context_object and __qmljs_get_imported_scripts functions and null pointer gets dereferenced, which leads to crash.

Both functions __qmljs_get_context_object and __qmljs_get_imported_scripts should return undefined in such case.

This http://pastebin.com/7kVvV6kr fixes the problem.