Merge pull request #32 from javier-marchena-hurtado/patch-2

Update papers_finder.py for error in Mattermost integration

Author: VladimirShitov

src/PaperBee/papers/papers_finder.py

@@ -371,6 +371,7 @@ async def run_daily(
         response_slack = None
         response_telegram = None
         response_zulip = None
+        response_mattermost = None
 
         if post_to_slack:
             response_slack = self.post_paper_to_slack(papers)