fixed input parameters

app.py

@@ -20,10 +20,12 @@ def process_image(input_image, model_name, conf):
     print(f"conf : {conf}")
 
     if model_name is None:
-        model_name = model_names[0]
+        return None, "No objects detected."
+#        model_name = model_names[0]
 
     if conf is None:
-        conf = 0.6
+        return None, "No objects detected."
+#        conf = 0.6
 
     model_index = model_names.index(model_name)
     print('model_index: ')