prevent crash when hiding debug windows

[Geokureli]

While it's still not recommended to call FlxG.save.bind, this prevents a crash when you hide a debug window while using a custom save path on FlxG.save.

Note: if you set FlxG.save to a custom path after the FlxGame is created, you'll still have other problems, since you're saving flixel settings to a different file than the one you're loading. This just prevents a crash.

It's still recommended to either

1. use the default path and never call bind on FlxG.save
2. call FlxG.save.bind before the FlxGame constructor is called
3. use a different FlxSave instance than FlxG.save to save your game data and let flixel use FlxG.save for built in features

[chosencharacters]

<3