Update app.py

app.py

@@ -10,7 +10,7 @@ app_choice = os.getenv("APP_CHOICE", "simple_app")
 
 if app_choice == "adv_app" and os.path.exists("adv_app.py"):
     from adv_app import *
-elif app == "simple_app" and os.path.exists("simple_app.py"):
+elif app_choice == "simple_app" and os.path.exists("simple_app.py"):
     from simple_app import *
 else:
     from tuner import *