[gnome-music/wip/mschraal/grltrackerwrapper-check-smart-playlist-crash] grltrackerwrapper: Fix early playlists change check crash

[Marinus Schraal <mschraal src gnome org>]

commit c9947756b4b7ace7aa9096bf4c165ad84d47a987
Author: Marinus Schraal <mschraal gnome org>
Date:   Thu Apr 16 15:53:18 2020 +0200

    grltrackerwrapper: Fix early playlists change check crash
    
    In 41c60ec7c3 the playlist wrapper creation gets delayed until after the
    initial songs list has filled. It is now possible however that on larger
    collections change tracking is already starting on the songs list before the
    playlist wrapper is loaded. This can cause a crash when checking for
    smart playlist changes on an uninitialized GrlTrackerPlaylists object.
    
    Add a check for existence of the GrlTrackerPlaylists object to avoid
    this.
    
    Fixes: #382

 gnomemusic/grilowrappers/grltrackerwrapper.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/gnomemusic/grilowrappers/grltrackerwrapper.py b/gnomemusic/grilowrappers/grltrackerwrapper.py
index 4997640e..4a4bcc52 100644
--- a/gnomemusic/grilowrappers/grltrackerwrapper.py
+++ b/gnomemusic/grilowrappers/grltrackerwrapper.py
@@ -159,7 +159,8 @@ class GrlTrackerWrapper(GObject.GObject):
 
         self._check_album_change()
         self._check_artist_change()
-        self._tracker_playlists.check_smart_playlist_change()
+        if self._tracker_playlists is not None:
+            self._tracker_playlists.check_smart_playlist_change()
 
         self._batch_changed_media_ids = {}
         self._content_changed_timeout = None