Fix incorrect trace of post-accumulate grad hook on tensor with zero …

…dimensions

pytorch#135226

Change-Id: Ic23442910ebe217a14a1762a78d0195b13d80111

torch/_dynamo/compiled_autograd.py

@@ -199,13 +199,13 @@ def post_acc_grad_hook(self, input, hook_id):
         assert isinstance(input, torch.Tensor)
         assert self.hooks_proxy is not None
         hook = self.hooks_proxy[hook_id]  # type: ignore[index]
-        proxies = self.proxy_call_hook(
+        proxy = self.proxy_call_hook(
             hook,
             input,
         )
         with disable_proxy_modes_tracing():
             input = [maybe_clone(input)]
-            self.bind_tensors_to_proxies(input, proxies)
+            self.bind_tensors_to_proxies(input, [proxy])
         return input
 
     # Note: [Compiled autograd and cudagraphs]