[FIX] website: disable preview on dynamic snippet filter selection

Before this commit filter selection on the dynamic snippet did trigger
the rendering of a preview. This sometimes caused a blocking loader to
appear when the filter selection triggered the replacement of the list
of available templates.

After this commit selecting a filter does not trigger a preview
rendering anymore.
Also the condition for making the warning message appear is now about
the selected template being in the list of available templates.

https://github.com/odoo/odoo/pull/68529

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

@@ -74,10 +74,10 @@ const dynamicSnippetOptions = options.Class.extend({
      */
     _refreshPublicWidgets: function () {
         return this._super.apply(this, arguments).then(() => {
-            const templateKeys = this.$el ? this.$el.find("we-select[data-attribute-name='templateKey'] we-selection-items we-button") : [];
+            const selectedTemplateId = this.$target.get(0).dataset['templateKey'];
             this.$target.find('.missing_option_warning').toggleClass(
                 'd-none',
-                templateKeys.length > 0
+                !!this.dynamicFilterTemplates[selectedTemplateId]
             );
         });
     },

addons/website/views/snippets/s_dynamic_snippet.xml

@@ -19,7 +19,7 @@
     </template>
     <template id="website.s_dynamic_snippet_options_template">
         <div t-attf-data-js="#{snippet_name}" t-attf-data-selector="#{snippet_selector}" data-no-preview="true">
-            <we-select string="Filter" data-name="filter_opt" data-attribute-name="filterId">
+            <we-select string="Filter" data-name="filter_opt" data-attribute-name="filterId" data-no-preview="true">
             </we-select>
             <we-select string="Template" data-name="template_opt" data-attribute-name="templateKey" data-no-preview="true">
             </we-select>