sane-tag-music: rewrite empty tracknumber tag to delete the tracknumber tag

pkgs/additional/sane-scripts/src/sane-tag-music

@@ -162,6 +162,7 @@ class Tags:
                     if int(trackno) <= int(last):
                         self.tracknumber[i] = trackno.lstrip('0')
                 except: pass
+        self.tracknumber = [ t for t in self.tracknumber if t != '' ]
 
     def expand_shorthands(self) -> None:
         va = ["V.A.", "Various"]