FIX: Don't attempt to delete non-existent bookmark (#12473)

Could happen when using the keyboard shortcut. ("d d")

app/assets/javascripts/discourse/app/components/bookmark.js

@@ -383,6 +383,10 @@ export default Component.extend({
 
   @action
   delete() {
+    if (!this.model.id) {
+      return;
+    }
+
     this._deleting = true;
     let deleteAction = () => {
       this._closeWithoutSaving = true;