Update web_demo_streamlit-minicpmv2_6.py

1. Avoid using 'None' string when `user_text` is empty.
2. Added `st.spinner` to display a loading message during AI content generation.

web_demo_streamlit-minicpmv2_6.py

@@ -173,9 +173,13 @@ def encode_video(video_path):
     return frames
 
 
+
 # User input box
 user_text = st.chat_input("Enter your question")
-if user_text:
+if user_text is not None:
+    if user_text.strip() is "":
+        st.warning('Input message could not be empty!', icon="⚠️")
+    else:
         # Display user input and save it to session history
         with st.chat_message(U_NAME, avatar="user"):
             st.session_state.chat_history.append({
@@ -251,6 +255,7 @@ if user_text:
             print("params:", params)  # debug
 
             # Generate and display the model's responses
+            with st.spinner('AI is thinking...'):
                 response = model.chat(image=None, msgs=msgs, context=None, tokenizer=tokenizer, **params)
             st.session_state.response = st.write_stream(response)
             st.session_state.chat_history.append({
@@ -261,3 +266,4 @@ if user_text:
             })
 
         st.divider()  # Add separators to the interface
+