Fix now playing playlist not highlighting selected item on initial open

[Joehuu]

Before:

After:

[bdach]

This is really convoluted and haphazard. Note that after the BindValueChanged() call, which calls updateSelectionState(instant: false), updateSelectionState(instant: true) is called. There's no reason why you would issue a non-instant update and then an instant update. This fix only appears to work because the (..., true) change happens to update the initial state of the selected field which is not valid on master. There's also the part where even if updateSelectionState() is hit, the text sprites of the title part may not have been created yet. So this pretty much only works by chance.

If you ask me, this pull should look like this:

diff --git a/osu.Game/Overlays/Music/PlaylistItem.cs b/osu.Game/Overlays/Music/PlaylistItem.cs
index 00c5ce8002..4a39cc06c8 100644
--- a/osu.Game/Overlays/Music/PlaylistItem.cs
+++ b/osu.Game/Overlays/Music/PlaylistItem.cs
@@ -56,7 +56,7 @@ protected override void LoadComplete()
                 var artist = new RomanisableString(metadata.ArtistUnicode, metadata.Artist);
 
                 titlePart = text.AddText(title, sprite => sprite.Font = OsuFont.GetFont(weight: FontWeight.Regular));
-                titlePart.DrawablePartsRecreated += _ => updateSelectionState(true);
+                titlePart.DrawablePartsRecreated += _ => updateSelectionState(SelectedSet.Value, instant: true);
 
                 text.AddText(@"  "); // to separate the title from the artist.
                 text.AddText(artist, sprite =>
@@ -66,25 +66,22 @@ protected override void LoadComplete()
                     sprite.Padding = new MarginPadding { Top = 1 };
                 });
 
-                SelectedSet.BindValueChanged(set =>
-                {
-                    bool newSelected = set.NewValue?.Equals(Model) == true;
-
-                    if (newSelected == selected)
-                        return;
-
-                    selected = newSelected;
-                    updateSelectionState(false);
-                });
-
-                updateSelectionState(true);
+                SelectedSet.BindValueChanged(set => updateSelectionState(set.NewValue, instant: false));
+                updateSelectionState(SelectedSet.Value, instant: true);
             });
         }
 
         private bool selected;
 
-        private void updateSelectionState(bool instant)
+        private void updateSelectionState(Live<BeatmapSetInfo> selectedSet, bool instant)
         {
+            bool newSelected = selectedSet?.Equals(Model) == true;
+
+            if (newSelected == selected && !instant) // instant updates should forcibly set correct state regardless of previous state.
+                return;
+
+            selected = newSelected;
+
             foreach (Drawable s in titlePart.Drawables)
                 s.FadeColour(selected ? colours.Yellow : Color4.White, instant ? 0 : FADE_DURATION);
         }