fix regenerate

app.py

@@ -88,8 +88,8 @@ def load_demo_refresh_model_list():
 
 def regenerate(state, image_process_mode):
     logging.info(f"regenerate.")
-    state.messages[-1][-1] = None
-    prev_human_msg = state.messages[-2]
+    state.messages = state.messages[:-3]
+    prev_human_msg = state.messages[-1]
     if type(prev_human_msg[1]) in (tuple, list):
         prev_human_msg[1] = (*prev_human_msg[1][:2], image_process_mode, *prev_human_msg[1][3:])
     state.skip_next = False