[FIX] website: image gallery do not open the media dialog if not empty

Do not auto open the media dialog after the drop if there are images in
snippets images wall and images gallery.

task-2312878

X-original-commit: ab2dacbb844b36793df891a844e89482cf12f14e

addons/website/static/src/snippets/s_image_gallery/options.js

@@ -57,7 +57,9 @@ options.registry.gallery = options.Class.extend({
      * @override
      */
     onBuilt: function () {
-        this.addImages(false);
+        if (this.$target.find('.o_add_images').length) {
+            this.addImages(false);
+        }
         // TODO should consider the async parts
         this._adaptNavigationIDs();
     },