Update app.py

app.py

@@ -14,8 +14,8 @@ def set_openai_api_key(api_key: str):
     """Set the api key and return chain.
     If no api_key, then None is returned.
     """
-    if os.environ["OPENAI_API_KEY"]:
-        os.environ["OPENAI_API_KEY"] = api_key
+    if api_key:
+        os.environ["OPENAI_API_KEY"] = os.environ["OPENAI_API_KEY"]
         chain = get_chain(vectorstore)
         os.environ["OPENAI_API_KEY"] = ""
         return chain