finishPropagationStep() {
    if (this.isStopped() || this._componentList.isRoot(this._componentId)) {
      this._previousPropagation = this._clone();
      this._reset();
    } else {
      this.previousPosition = this._position;
    }
  }
Ends handling of a propagation step and performs cleanup. Called as a after callback.
@returns {void}