[Bug 18824] Thief 3 crashes when starting a new game

http://bugs.winehq.org/show_bug.cgi?id=18824

--- Comment #15 from Stefan Dösinger   2009-06-08 12:16:42 ---
Can you check if there are any Unmap calls without a Map() call? That's
probably supposed to return an error, but we do not check for this condition
yet. If the buffer is unlocked without being locked, the lockcount gets
negative, and since it is an unsigned value that's a pretty large positive
value. Prior to my patch this probably kept the buffer working normally, maybe
the GL buffer wasn't updated properly, but no crash should occur. Now with the
glMapBuffer calls that means a NULL buffer data pointer and a crash.