fix: voice trigger not receiving audio from pymumble

pymumble passes a User object, not a dict. The isinstance(user, dict)
check returned False, setting name to None and silently discarding
every voice packet. Use try/except for dict-like access instead.

plugins/voice.py

@@ -86,7 +86,10 @@ def _on_voice(bot, user, sound_chunk):
     ps = _ps(bot)
     if not ps["listen"] and not ps["trigger"]:
         return
-    name = user["name"] if isinstance(user, dict) else None
+    try:
+        name = user["name"]
+    except (KeyError, TypeError):
+        name = None
     if not name or name == bot.nick:
         return
     pcm = sound_chunk.pcm