fix png

app.py

@@ -79,6 +79,8 @@ if img_file_buffer is None:
 if img_file_buffer is not None:
     # To read image file buffer as a PIL Image:
     img = Image.open(img_file_buffer)
+    if img.mode == 'RGBA':
+        img = img.convert('RGB')
     
     detected_face = mtcnn2(img)
     if detected_face is None: