Fix fail_if_not_exists not being set when constructed with state

discord/message.py

@@ -342,6 +342,7 @@ class MessageReference:
         self.message_id = utils._get_as_snowflake(data, 'message_id')
         self.channel_id = int(data.pop('channel_id'))
         self.guild_id = utils._get_as_snowflake(data, 'guild_id')
+        self.fail_if_not_exists = data.get('fail_if_not_exists', True)
         self._state = state
         self.resolved = None
         return self