lastgenre: fix crash with canonicalization

beetsplug/lastgenre/__init__.py

@@ -299,9 +299,10 @@ class LastGenrePlugin(plugins.BeetsPlugin):
                 return result, 'artist'
 
         # Filter the existing genre.
-        result = _strings_to_genre([obj.genre])
-        if result:
-            return result, 'original'
+        if obj.genre:
+            result = _strings_to_genre([obj.genre])
+            if result:
+                return result, 'original'
 
         # Fallback string.
         fallback = self.config['fallback'].get()

docs/changelog.rst

@@ -19,6 +19,7 @@ Changelog
 * :doc:`/plugins/web`: The underlying API was expanded slightly to support
   `Tomahawk`_ collections. And file transfers now have a "Content-Length"
   header. Thanks to Uwe L. Korn.
+* :doc:`/plugins/lastgenre`: Fix an error when using genre canonicalization.
 
 .. _Tomahawk: http://www.tomahawk-player.org/