- added explicit clearing of global VM stask

When exception is thrown from JITed code, VM stask isn't cleared during unwinding
It needs to be clear explicitly to avoid memory leaks and references to destructed objects on shutdown

https://forum.zdoom.org/viewtopic.php?t=66172

src/playsim/dthinker.cpp

@@ -250,6 +250,7 @@ void FThinkerCollection::DestroyAllThinkers()
 	GC::FullGC();
 	if (error)
 	{
+		ClearGlobalVMStack();
 		I_Error("DestroyAllThinkers failed");
 	}
 }