fix: ensure setting config.layout to nil manually still behaves the same

Author: ElMassimo

lib/inertia_rails/renderer.rb

@@ -46,7 +46,8 @@ def render_ssr
     end
 
     def layout
-      configuration.layout
+      layout = configuration.layout
+      layout.nil? ? true : layout
     end
 
     def shared_data