Fix module backward pre-hooks to actually update gradient (#97983)

Pull Request resolved: https://github.com/pytorch/pytorch/pull/97983
Approved by: https://github.com/albanD

torch/utils/hooks.py

@@ -223,6 +223,11 @@ class BackwardHook:
                             raise RuntimeError("Backward hook for Modules where no input requires "
                                                "gradient should always return None or None for all gradients.")
                     self.grad_outputs = None
+
+                if self.grad_outputs is not None:
+                    assert self.output_tensors_index is not None  # mypy
+                    return tuple(self.grad_outputs[i] for i in self.output_tensors_index)
+
             grad_fn.register_hook(hook)
 
         is_tuple = True