Avoid nullability compiler/clang-tidy warnings in _GTMDevAssert.
Avoid nullability compiler/clang-tidy warnings in _GTMDevAssert.

The string parameters in NSAssertionHandler's -handleFailureInFunction:… method are declared nonnull, but converting __PRETTY_FUNCTION__ and __FILE__ to NSString (via +[NSString stringWithUTF8String:] returns nullable, leading to warnings.

thomasvl/google-toolbox-for-mac,google/google-toolbox-for-mac,google/google-toolbox-for-mac,thomasvl/google-toolbox-for-mac