scrub: no need to save after delete()

The delete() method on Mutagen objects writes the file directly. Calling
save() was unnecessary and, in at least one case we found, could inadvertently
preserve non-standard tags that Mutagen did not understand.

beetsplug/scrub.py

@@ -127,12 +127,12 @@ def _scrub(path):
             # remove them. In this case, we just remove all the tags.
             for tag in f.keys():
                 del f[tag]
+            f.save()
         except IOError as exc:
             log.error(u'could not scrub {0}: {1}'.format(
                 util.displayable_path(path),
                 exc,
             ))
-        f.save()
 
 
 # Automatically embed art into imported albums.

docs/changelog.rst

@@ -56,6 +56,8 @@ And some fixes:
   Thanks to Pedro Silva.
 * Fix an occasional KeyError in the :ref:`update-cmd` command introduced in
   1.3.0.
+* :doc:`/plugins/scrub`: Avoid preserving certain non-standard ID3 tags such
+  as NCON.
 
 .. _Opus: http://www.opus-codec.org/
 .. _@Verrus: https://github.com/Verrus