fix key validation logic (#3936)

packages/rsx/src/template_body.rs

@@ -236,11 +236,13 @@ impl TemplateBody {
 
         // Assign paths to all nodes in the template
         body.assign_paths_inner(&nodes);
-        body.validate_key();
 
         // And then save the roots
         body.roots = nodes;
 
+        // Finally, validate the key
+        body.validate_key();
+
         body
     }