Switched `FlxG.safeDestroy` to `FlxDestroyUtil.destroy` so that it would actually work...
Minor fix in FlxNestedSprite - check if children is null before trying to destroy it.
Merge branch 'dev' of https://github.com/SeiferTim/flixel-addons into dev

Conflicts:
	flixel/addons/effects/FlxTrailArea.hx
FlxNestedSprite: small cleanup