Apply the default SampleControlPoint if not externally provided

This is mostly to handle tests for now, as generally this should be
provided by an external source in all other cases.

osu.Game/Rulesets/Objects/HitObject.cs

@@ -112,6 +112,10 @@ namespace osu.Game.Rulesets.Objects
                 // This is done here since ApplyDefaultsToSelf may be used to determine the end time
                 SampleControlPoint = legacyInfo.SamplePointAt(this.GetEndTime() + control_point_leniency);
             }
+            else
+            {
+                SampleControlPoint ??= SampleControlPoint.DEFAULT;
+            }
 
             nestedHitObjects.Clear();