Merge pull request scrapinghub#24 from jathanism/crashfix

Fix periodic crash when looking up username in dispatcher.

Author: lins05

slackbot/dispatcher.py

@@ -50,7 +50,7 @@ def _on_new_message(self, msg):
         try:
             msguser = self._client.users.get(msg['user'])
             username = msguser['name']
-        except KeyError:
+        except (KeyError, TypeError):
             if 'username' in msg:
                 username = msg['username']
             else: