Fix out of range exceptions due to out-of-order hitobjects.

osu.Game.Rulesets.Mania/Beatmaps/ManiaBeatmapConverter.cs

@@ -25,7 +25,8 @@ protected override Beatmap<ManiaHitObject> ConvertBeatmap(Beatmap original)
             {
                 BeatmapInfo = original.BeatmapInfo,
                 TimingInfo = original.TimingInfo,
-                HitObjects = original.HitObjects.SelectMany(converter.Convert).ToList()
+                // We need to sort here, because the converter generates patterns
+                HitObjects = original.HitObjects.SelectMany(converter.Convert).OrderBy(h => h.StartTime).ToList()
             };
         }