Merge pull request #17008 from stub42/yay_destructors

Handle missing globals in Python Channel destructors

src/python/grpcio/grpc/_channel.py

@@ -980,8 +980,9 @@ class Channel(grpc.Channel):
         # for as long as they are in use and to close them after using them,
         # then deletion of this grpc._channel.Channel instance can be made to
         # effect closure of the underlying cygrpc.Channel instance.
-        cygrpc.fork_unregister_channel(self)
+        if cygrpc is not None:  # Globals may have already been collected.
+            cygrpc.fork_unregister_channel(self)
         # This prevent the failed-at-initializing object removal from failing.
         # Though the __init__ failed, the removal will still trigger __del__.
-        if hasattr(self, "_connectivity_state"):
+        if _moot is not None and hasattr(self, "_connectivity_state"):
             _moot(self._connectivity_state)