Update app.py

app.py

@@ -24,7 +24,9 @@ example_list = [["examples/" + example] for example in os.listdir("examples")]
 
 def transfer(image, model):
     device = 'cpu'
-
+    if model is None:
+        model = '0'
+    
     width = image.size[0]
     height = image.size[1]