Avoid tracking hit events altogether during migration

osu.Game/Database/StandardisedScoreMigrationTools.cs

@@ -21,6 +21,8 @@ namespace osu.Game.Database
             var ruleset = score.Ruleset.CreateInstance();
             var processor = ruleset.CreateScoreProcessor();
 
+            processor.TrackHitEvents = false;
+
             var beatmap = new Beatmap();
 
             HitResult maxRulesetJudgement = ruleset.GetHitResults().First().result;

osu.Game/Rulesets/Scoring/ScoreProcessor.cs

@@ -30,6 +30,11 @@ namespace osu.Game.Rulesets.Scoring
         private const double accuracy_cutoff_c = 0.7;
         private const double accuracy_cutoff_d = 0;
 
+        /// <summary>
+        /// Whether <see cref="HitEvents"/> should be populated during application of results.
+        /// </summary>
+        internal bool TrackHitEvents = true;
+
         /// <summary>
         /// Invoked when this <see cref="ScoreProcessor"/> was reset from a replay frame.
         /// </summary>
@@ -226,7 +231,7 @@ namespace osu.Game.Rulesets.Scoring
 
             ApplyScoreChange(result);
 
-            if (!IsSimulating)
+            if (!IsSimulating && TrackHitEvents)
             {
                 hitEvents.Add(CreateHitEvent(result));
                 lastHitObject = result.HitObject;