sidebar: add_to_playlist() fixes

- Commit after adding tracks
- If tracks were added to the Queued Tracks playlist, then set it as the
  current playlist in the Player

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

sidebar/__init__.py

@@ -1,4 +1,5 @@
 # Copyright 2021 (c) Anna Schumaker.
+import audio
 import db
 from gi.repository import Gtk
 from . import stack
@@ -25,3 +26,6 @@ class Sidebar(Gtk.Box):
         if playlist.can_add_remove_tracks():
             for track in self.panel.selected_tracks():
                 playlist.add_track(track)
+            if playlist == db.user.Table.find("Queued Tracks"):
+                audio.Player.set_playlist(playlist)
+            db.sql.commit()