如果有字幕，则将类添加到featherlight

Question

仅在未添加div或未向featherlight-content包装器中添加类的情况下，才显示添加了标题的featherlight标题div

$.featherlightGallery.prototype.afterContent = function() {
    var caption = this.$currentTarget.find('img').attr('alt');
    this.$instance.find('.caption').remove();
    $('<div class="caption">').text(caption).appendTo(this.$instance.find('.featherlight-content'));
};