Update track.lastplayed field

Fixes #78

app/model.py

@@ -106,7 +106,7 @@ class Playdates(Base):
         pd.lastplayed = datetime.now()
         pd.track_id = track.id
         session.add(pd)
-        track.update_lastplayed()
+        track.update_lastplayed(session, track.id)
         session.commit()
 
     @staticmethod
@@ -596,8 +596,11 @@ class Tracks(Base):
         return session.query(Tracks).filter(
             Tracks.id == id).one()
 
-    def update_lastplayed(self):
-        self.lastplayed = datetime.now()
+    @staticmethod
+    def update_lastplayed(session, track_id):
+        track = session.query(Tracks).filter(Tracks.id == track_id).one()
+        track.lastplayed = datetime.now()
+        session.commit()
 
     @staticmethod
     def update_artist(session, track_id, artist):

app/musicmuster.py

@@ -511,7 +511,6 @@ class Window(QMainWindow, Ui_MainWindow):
                                     QColor(Config.COLOUR_NEXT_TAB))
 
             # Tell database to record it as played
-            self.current_track.update_lastplayed()
             Playdates.add_playdate(session, self.current_track)
 
             self.disable_play_next_controls()