Add a condition for nested_detach (#31855)

fix bug: https://github.com/huggingface/transformers/issues/31852

src/transformers/trainer_pt_utils.py

@@ -192,7 +192,7 @@ def nested_detach(tensors):
         return type(tensors)(nested_detach(t) for t in tensors)
     elif isinstance(tensors, Mapping):
         return type(tensors)({k: nested_detach(t) for k, t in tensors.items()})
-    return tensors.detach()
+    return tensors.detach() if isinstance(tensors, torch.Tensor) else tensors
 
 
 def nested_xla_mesh_reduce(tensors, name):