Possible netgame quit crash hotfix

This possibly fixes #487 (closed), it seems that the game does not properly flag "revert" strings of consvars as not allocated in zone memory anymore when it frees them to set a new value. And if that new value is not in zone memory, it then tries to free that and possibly comes up with the "wrong id" error as a result.

This is all just my guesswork though, I haven't actually tested this fix out yet so I don't know if it works.