Update app.py

app.py

@@ -150,8 +150,8 @@ def question_answer(url, file, question, openAI_key, model):
     if url.strip() != '' and file != None:
         return '[ERROR]: Both URL and PDF is provided. Please provide only one (either URL or PDF).'
     
-    if model is None:
-        return '[ERROR]: You have not selected any model. Please select an LLM model.'
+    if model is None or model =='':
+        return '[ERROR]: You have not selected any model. Please choose an LLM model.'
         
     if url.strip() != '':
         glob_url = url