Update app.py

app.py

@@ -174,6 +174,10 @@ model = HfApiModel(
     custom_role_conversions=None,
 )
 
+# Patch: Ensure last_input_token_count is initialized to 0 if not already set.
+if model.last_input_token_count is None:
+    model.last_input_token_count = 0
+
 # Import tool from Hub
 image_generation_tool = load_tool("agents-course/text-to-image", trust_remote_code=True)