[2020] Common Heist Freeze/Crash fixed

So we just fixed by far the most common crash/freeze that was occurring in Heists. If you were stockpiling contracts to avoid losing them to this bug, it should be okay to play them now.

There are still many other issues we're working through including other crashes, and we'll get those out as soon as we can. Specifically there's a client crash that occurs in Predictive mode that we're working on a fix for now. I have been keeping the weekend hotfix thread up to date.