Improve type hints for webhook implementation in dialogflow (#121592)

homeassistant/components/dialogflow/__init__.py

@@ -28,7 +28,9 @@ class DialogFlowError(HomeAssistantError):
     """Raised when a DialogFlow error happens."""
 
 
-async def handle_webhook(hass, webhook_id, request):
+async def handle_webhook(
+    hass: HomeAssistant, webhook_id: str, request: web.Request
+) -> web.Response | None:
     """Handle incoming webhook with Dialogflow requests."""
     message = await request.json()
 
@@ -36,7 +38,7 @@ async def handle_webhook(hass, webhook_id, request):
 
     try:
         response = await async_handle_message(hass, message)
-        return b"" if response is None else web.json_response(response)
+        return None if response is None else web.json_response(response)
 
     except DialogFlowError as err:
         _LOGGER.warning(str(err))