Update Gradio_UI.py

Gradio_UI.py

@@ -143,10 +143,10 @@ def stream_to_gradio(
         # Track tokens if model provides them
         if hasattr(agent.model, "last_input_token_count"):
             total_input_tokens += agent.model.last_input_token_count or 0
-            total_output_tokens += agent.model.last_output_token_count
+            total_output_tokens += agent.model.last_output_token_count or 0  
             if isinstance(step_log, ActionStep):
-                step_log.input_token_count = agent.model.last_input_token_count
-                step_log.output_token_count = agent.model.last_output_token_count
+                step_log.input_token_count = agent.model.last_input_token_count or 0
+                step_log.output_token_count = agent.model.last_output_token_count or 0   
 
         for message in pull_messages_from_step(
             step_log,