Fix InvalidStateError in MessageQueue when the IRC server closes the connection

http2irc.py

@@ -172,12 +172,12 @@ class MessageQueue:
 
 	def put_nowait(self, item):
 		self._queue.append(item)
-		if self._getter is not None:
+		if self._getter is not None and not self._getter.cancelled():
 			self._getter.set_result(None)
 
 	def putleft_nowait(self, *item):
 		self._queue.extendleft(reversed(item))
-		if self._getter is not None:
+		if self._getter is not None and not self._getter.cancelled():
 			self._getter.set_result(None)
 
 	def qsize(self):