fixed artist paging

app.py

@@ -516,11 +516,17 @@ class ArtistsGUI(Screen):
         if self.page - 1 <= 0:
             return
 
+        # Count artist panels with info in them
+        real_displayed = 0
+        for artist_panel in artist_panels:
+            if artist_panel.artist:
+                real_displayed += 1
+
         self.page -= 1
         self.update_pager()
         self._clear_panels()
 
-        self.artists_displayed -= len(artist_panels) * 2
+        self.artists_displayed -= len(artist_panels) + real_displayed
         for artist_panel in artist_panels:
             artist_panel.set_artist(self.artists[self.artists_displayed])
             self.artists_displayed += 1