[CHORE] Fix a null safety error in MusicTimeChangeEvent.hx#2

ADA-Funni wants to merge 1 commit intoPurSnake:mainPurSnake/FlxRhythmConductor:mainfrom

ADA-Funni:chore/ease-function-nullsafety-go-brrrADA-Funni/FlxRhythmConductor:chore/ease-function-nullsafety-go-brrrCopy head branch name to clipboard