function crossCheckFilter(tweenProp) {
    var this$1$1 = this;

    if (this.valuesEnd[tweenProp]) {
      Object.keys(this.valuesStart[tweenProp]).forEach(function (fn) {
        if (!this$1$1.valuesEnd[tweenProp][fn]) {
          this$1$1.valuesEnd[tweenProp][fn] = this$1$1.valuesStart[tweenProp][fn];
        }
      });
    }
  }
Adds missing sub-properties in `valuesEnd` from `valuesStart`.
@param {string} tweenProp the property name