toMap method Null safety

Implementation

@override
Map<String, Object?> toMap() {
  return {
    'animate': this.animate,
    'delay': this.delay,
    'duration': this.duration,
    'fromValue': this.fromValue,
    'toValue': this.toValue,
    'easingCurve': this.easingCurve?.index,
    'trackMove': this.trackMove,
  };
}