_loadMaskFile(event) {
    let imgUrl;

    if (!isSupportFileApi()) {
      alert('This browser does not support file-api');
    }

    const [file] = event.target.files;

    if (file) {
      imgUrl = URL.createObjectURL(file);
      this.actions.loadImageFromURL(imgUrl, file);
      this._els.applyButton.classList.add('active');
    }
  }
Load mask file
@param {object} event - File change event object
@private