[FIX] website: fix background video placement in popup

Before this commit, if you add a background video in a popup, the video
frame will not setup properly because the _adjustIframe function cannot
find wrapperWidth and its ratio.

After this commit, _adjustIframe will be called again once the popup
is opened.

task-2251203

Part-of: odoo/odoo#63634
Co-authored-by: qsm-odoo <qsm@odoo.com>

addons/website/static/src/js/content/snippets.animation.js

@@ -682,6 +682,18 @@ registry.backgroundVideo = publicWidget.Widget.extend({
 
         $(window).on('resize.' + this.iframeID, throttledUpdate);
 
+        const $modal = this.$target.closest('.modal');
+        if ($modal.length) {
+            $modal.on('show.bs.modal', () => {
+                const videoContainerEl = this.$target[0].querySelector('.o_bg_video_container');
+                videoContainerEl.classList.add('d-none');
+            });
+            $modal.on('shown.bs.modal', () => {
+                this._adjustIframe();
+                const videoContainerEl = this.$target[0].querySelector('.o_bg_video_container');
+                videoContainerEl.classList.remove('d-none');
+            });
+        }
         return Promise.all(proms).then(() => this._appendBgVideo());
     },
     /**