Fix mod perfect test scenes failing due to null ruleset provided

Just a workaround for now, a better fix may be to put the test data creation in an action that is guaranteed to be invoked after the test scene has fully loaded (all dependencies would've been resolved by then).

osu.Game/Tests/Visual/ModPerfectTestScene.cs

@@ -22,7 +22,7 @@ namespace osu.Game.Tests.Visual
             Mod = mod,
             Beatmap = new Beatmap
             {
-                BeatmapInfo = { Ruleset = Ruleset.Value },
+                BeatmapInfo = { Ruleset = CreatePlayerRuleset().RulesetInfo },
                 HitObjects = { testData.HitObject }
             },
             Autoplay = !shouldMiss,