When compiled in release mode with GCC 6, QtQml crashes. This option
gets works around the issue by instructing the compiler not to delete
null pointer checks for pointers that the standard says cannot be null,
yet apparently are.

This is a temporary workaround until a proper solution is found.

Change-Id: Id3aab65533904562a6cbfffd14501a185fc91179
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>