[FIX] website: fix map snippet saved

This commit fixes the issue of having duplicate iframes when dropping a
custom "s_map" snippet that has been saved by the user.

This issue was introduced by this commit [1].

Steps to reproduce the bug:
- Drag and drop a "s_map" snippet onto the page.
- Save this "s_map" snippet by clicking on the custom snippet "save"
button.
- Drag and drop the saved snippet onto the page.
- Observe that a duplicate iframe is created in the snippet.

This commit adds a check to verify if an iframe already exists before
adding it when dropping a "s_map" snippet.

[1]: https://github.com/odoo/odoo/commit/88194dd94182ad1bbdcb9aa8f855f30f6369d148



task-3340644

closes odoo/odoo#122645

Signed-off-by: Romain Derie (rde) <rde@odoo.com>

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

@@ -9,9 +9,15 @@ options.registry.Map = options.Class.extend({
      * @override
      */
     onBuilt() {
-        const iframeEl = generateGMapIframe();
-        this.$target[0].querySelector('.s_map_color_filter').before(iframeEl);
-        this._updateSource();
+        // The iframe is added here to the snippet when it is dropped onto the
+        // page. However, in the case where a custom snippet saved by the user
+        // is dropped, the iframe already exists and doesn't need to be added
+        // again.
+        if (!this.$target[0].querySelector('.s_map_embedded')) {
+            const iframeEl = generateGMapIframe();
+            this.$target[0].querySelector('.s_map_color_filter').before(iframeEl);
+            this._updateSource();
+        }
     },
 
     //--------------------------------------------------------------------------