I download the MDB-Pro_4.19.1.zip form the my account "order section", after un-zip it, in the templates folder there is a about-us.html page, in that page, there is a lightbox gallery area, but when I click on the image, the error shows:

mdb.min.js:1 Uncaught TypeError: Cannot read property 'firstChild' of undefined at Object.getChildByClass (mdb.min.js:1) at Object.init (mdb.min.js:1) at i (mdb.min.js:1) at HTMLDivElement.e (mdb.min.js:1)

I also record a video here: http://2020.dowebs.co/video.mp4

Thanks

`

                    <div id="mdb-lightbox-ui"></div>

                    <div class="mdb-lightbox">

                        <figure class="col-md-4">
                            <a href="https://mdbootstrap.com/img/Photos/Horizontal/Work/12-col/img%20(43).jpg" data-size="1600x1067">
                                <img src="https://mdbootstrap.com/img/Photos/Horizontal/Work/12-col/img%20(43).jpg" class="img-fluid z-depth-1" />
                            </a>
                        </figure>

                        <figure class="col-md-4">
                            <a href="https://mdbootstrap.com/img/Photos/Horizontal/Work/12-col/img%20(41).jpg" data-size="1600x1067">
                                <img src="https://mdbootstrap.com/img/Photos/Horizontal/Work/6-col/img%20(41).jpg" class="img-fluid z-depth-1" />
                            </a>
                        </figure>


                    </div>

                </div>

$(function () { $("#mdb-lightbox-ui").load("mdb-addons/mdb-lightbox-ui.html"); });

`