PB-266: Video background for Slide

- fix invalid video error

Author: omiroshnichenko

app/code/Magento/PageBuilder/view/adminhtml/web/js/content-type/slide/preview.js

@@ -138,7 +138,7 @@ export default class Preview extends BasePreview {
                     },
                 );
                 // @ts-ignore
-                this.wrapper.jarallax.video.on("started", () => {
+                this.wrapper.jarallax.video && this.wrapper.jarallax.video.on("started", () => {
                     // @ts-ignore
                     if (this.wrapper.jarallax.$video) {
                         // @ts-ignore