Upgrade the weights loading method to avoid duplicated loading.

app.py

@@ -52,6 +52,7 @@ birefnet.eval()
 
 @spaces.GPU
 def predict(image, resolution, weights_file):
+    global birefnet
     if weights_file != 'General':
         # Load BiRefNet with chosen weights
         _weights_file = '/'.join(('zhengpeng7', usage_to_weights_file[weights_file] if weights_file is not None else 'BiRefNet'))