better handle empty array

app.py

@@ -13,7 +13,10 @@ def chat(message, history):
     # append the new user input tokens to the chat history
     f1 = lambda x: x[2]
     f2 = lambda x: x[3]
-    bot_input_ids = torch.IntTensor([f(item) for item in history for f in (f1, f2)])
+    if len(history) > 0:
+        bot_input_ids = torch.IntTensor([f(item) for item in history for f in (f1, f2)])
+    else:
+        bot_input_id = torch.IntTensor([])
     print("BOT iDS", bot_input_ids)
     bot_input_ids = torch.cat([bot_input_ids, new_user_input_ids], dim=-1)  if bot_input_ids is not None else new_user_input_ids
     # generated a response while limiting the total chat history to 1000 tokens,