stdpy: protect against thread error when interpreter shuts down

direct/src/stdpy/thread.py

@@ -221,6 +221,10 @@ def _get_thread_locals(thread, i):
 def _remove_thread_id(threadId):
     """ Removes the thread with the indicated ID from the thread list. """
 
+    # On interpreter shutdown, Python may set module globals to None.
+    if _threadsLock is None or _threads is None:
+        return
+
     _threadsLock.acquire()
     try:
         thread, locals, wrapper = _threads[threadId]