Fixes a sporadic crash that occurred when exiting a program using a PinDMD. The crash was due to a timing issue (technically a thread race condition), so it occurred randomly. (See issue freezy#169.)
The crash was originally observed with a PinDMD v2 with PinballY, but can happen in any host application using the DLL. The corresponding code for PinDMD v1 and v3 both had the same error, so the crash probably affected them as well. This patch has fixes for all three device versions.
This is a patch to freezy's official 1.7.2 release. It should otherwise be identical to 1.7.2.