Ensure powerwall config flow title_placeholders items are [str, str] (h…

…ome-assistant#127205)

homeassistant/components/powerwall/config_flow.py

@@ -188,9 +188,9 @@ async def async_step_confirm_discovery(
     ) -> ConfigFlowResult:
         """Confirm a discovered powerwall."""
         assert self.ip_address is not None
+        assert self.title is not None
         assert self.unique_id is not None
         if user_input is not None:
-            assert self.title is not None
             return self.async_create_entry(
                 title=self.title,
                 data={