fixed responce synthesizer problem

app.py

@@ -23,10 +23,18 @@ def answer_question(question, history):
     try:
         start_time = time.time()
         
+        custom_prompt_template = PromptTemplate(CUSTOM_PROMPT_NEW)
+
+        response_synthesizer = get_response_synthesizer(
+            response_mode=ResponseMode.TREE_SUMMARIZE,
+            text_qa_template=custom_prompt_template
+        )
+
+
         if chat_engine is None:
             chat_engine = CondensePlusContextChatEngine.from_defaults(
                 retriever=query_engine.retriever,
-                response_synthesizer=query_engine.response_synthesizer
+                response_synthesizer=response_synthesizer,
             )
         
         response = chat_engine.chat(question)