fix: restore Load() try-catch fallback in RulesetShaderManager and mark flaky test

Author: Copilot

osu.Game.Tests/Visual/Ranking/TestSceneSoloResultsScreen.cs

@@ -172,6 +172,7 @@ public void TestOnlineLeaderboardWithLessThan50Scores()
             AddUntilStep("local score is #16", () => this.ChildrenOfType<ScorePanelList>().Single().GetPanelForScore(localScore).ScorePosition.Value, () => Is.EqualTo(16));
         }
 
+        [FlakyTest]
         [Test]
         public void TestOnlineLeaderboardWithLessThan50Scores_UserWasInTop50()
         {

osu.Game/Rulesets/UI/DrawableRulesetDependencies.cs

@@ -209,6 +209,18 @@ public RulesetShaderManager(IRenderer renderer, NamespacedResourceStore<byte[]>
                 this.parent = parent;
             }
 
+            public override IShader Load(string vertex, string fragment)
+            {
+                try
+                {
+                    return base.Load(vertex, fragment);
+                }
+                catch (FileNotFoundException)
+                {
+                    return parent.Load(vertex, fragment);
+                }
+            }
+
             public override IShader? GetCachedShader(string vertex, string fragment) => base.GetCachedShader(vertex, fragment) ?? parent.GetCachedShader(vertex, fragment);
 
             public override IShaderPart? GetCachedShaderPart(string name) => base.GetCachedShaderPart(name) ?? parent.GetCachedShaderPart(name);