FlxSpriteGroup: if you turn out outlines in the debugger, drawDebug() fa...

...ils on a null check because _point and _rect do not exist and are assumed to exist in FlxObject.drawDebug().

The overriden initVars() function in FlxSpriteGroup implies that these variables were excluded because they are not otherwise used by FlxSpriteGroup; Therefore, I added a compiler conditional that only creates them if the debugger overlay is available.