Ignore statistics update subscriptions with invalid score ID

If score submission fails, the score will not receive a correct online
ID from web, but will still be passed on to the solo statistics watcher
on the results screen. This could lead to the watcher subscribing to
changes with score ID equal to the default of -1. If this happened more
than once, that would cause a crash due to duplicate keys in the
`callbacks` dictionary.

Closes #21837.

osu.Game/Online/Solo/SoloStatisticsWatcher.cs

@@ -51,7 +51,7 @@ public void RegisterForStatisticsUpdateAfter(ScoreInfo score, Action<SoloStatist
             if (!api.IsLoggedIn)
                 return;
 
-            if (!score.Ruleset.IsLegacyRuleset())
+            if (!score.Ruleset.IsLegacyRuleset() || score.OnlineID <= 0)
                 return;
 
             var callback = new StatisticsUpdateCallback(score, onUpdateReady);