ScaleManager depends on "if (Null)" for isFullScreen

In Dart, if (Null) and if (!Null) cause type errors.

ScaleManager depends on !isFullScreen evaluating like isFullScreen == Null in at least one line of code.

If the following lines of code are placed in the preload() method for a State implementer:

game.scale.scaleMode = ScaleManager.SHOW_ALL;
game.scale.setScreenSize(false);

A type error occurs at line 1108 in scale_manager.dart:
} else if (!this.isFullScreen) {

isFullScreen should probably be initialized to false.