Update app.py

app.py

@@ -25,7 +25,10 @@ def dpt_large_inference(img):
     
 @spaces.GPU
 def infer(img):
-  return dpt_large_inference(img), dpt_beit_inference(img), depth_anything_inference(img)
+  if img is None:
+      return None, None, None
+  else:
+      return dpt_large_inference(img), dpt_beit_inference(img), depth_anything_inference(img)
 
 
 css = """