Don't bother using a channel state in __del__

If the channel is being deleted, we don't need to care about the state. Furthermore, if the channel is being deleted as Python is shutting down, _States will have been deleted (or set to None), so we can't access it. Rather than trying to work around the garbage collection, we just set it to None and call it a day.

src/channels.py

@@ -17,7 +17,6 @@ class _States(Enum):
     PendingLeave = "pending leave"
     Left = "left channel"
 
-    Deleted = "deleted"
     Cleared = "cleared"
 
 # This is used to tell if this is a fake channel or not. If this
@@ -71,7 +70,7 @@ class Channel(IRCContext):
     def __del__(self):
         self.users.clear()
         self.modes.clear()
-        self.state = _States.Deleted
+        self.state = None
         self.client = None
         self.timestamp = None