Fix exception when creating blank/invalid TimeSet sign mc1232

Since that last one was kind of non-constructive, here's a real one: Creating a blank mc1232 causes an exception on create and break.

Attempted fix, please tell me if changing the "think" method to refer to its state was valid or not because I didn't really look too far into it, and it seems weird that it should be different in the original. --edit-- and I don't see how self-triggered time set works either.