Thanks for reporting this!
This error only seems to happen when calling an Easy Tween at the VERY START of the game.
You can get around this by delaying the call by one step, or you could modify TweenEasyScale (and other easy scripts).
You would need to change:
if (!instance_exists(o_SharedTweener)) SharedTweener();
to :
SharedTweener();
I'll aim to include this change in the next beta release. I'm aiming for one this weekend.
-Stephen