Make mat2 more robust wrt. weird audio files

libmat2/audio.py

@@ -21,7 +21,7 @@ class MutagenParser(abstract.AbstractParser):
     def get_meta(self) -> Dict[str, Union[str, dict]]:
         f = mutagen.File(self.filename)
         if f.tags:
-            return {k:', '.join(v) for k, v in f.tags.items()}
+            return {k:', '.join(map(str, v)) for k, v in f.tags.items()}
         return {}
 
     def remove_all(self) -> bool: