Various: Work around msg.prefix in inFilter() potentially being empty...

...in Limnoria running on Python 3, particularly on startup.

* Bugtracker
* Encyclopedia
* PackageInfo

Bugtracker/plugin.py

@@ -238,6 +238,8 @@ class Bugtracker(callbacks.PluginRegexp):
     list = wrap(list, [additional('text')])
 
     def inFilter(self, irc, msg):
+        if not msg.prefix:
+            return msg
         if not defaultIgnored(msg.prefix, msg.args[0]):
             return msg
         if checkIgnored(msg.prefix, msg.args[0]):