`Check failed` in `tf.raw_ops.UnbatchGrad` when the input of `original_input` is empty.
@xl1043237213,
I was able to reproduce the issue on TensorFlow v2.15, [v2.16](https://colab.research.google.com/gist/tilakrayal/0461ab61356c744575934ecba7116d29/untitled1905.ipynb) and tf-nightly. Kindly find the gist of it [here](https://colab.research.google.com/gist/tilakrayal/bf5b58fbc42531de76cb219ad2aab98d/-6_tf_raw_ops_unbatchgrad.ipynb).

![image](https://github.com/tensorflow/tensorflow/assets/81610181/e26d1401-526c-4734-b5e0-dc413b84ba3a)

### Issue type

Bug

### Have you reproduced the bug with TensorFlow Nightly?

Yes

### Source

binary

### TensorFlow version

tf 2.15

### Custom code

No

### OS platform and distribution

Linux Ubuntu 20.04

### Mobile device

_No response_

### Python version

3.10

### Bazel version

_No response_

### GCC/compiler version

_No response_

### CUDA/cuDNN version

_No response_

### GPU model and memory

_No response_

### Current behavior?

When the input of `original_input` is empty,  `tf.raw_ops.UnbatchGrad` will trigger `Check failed` of the input tensor dimension.

### Standalone code to reproduce the issue

```shell
https://colab.research.google.com/drive/1ekseH5mJBvt3_SeK4MuAAM47U8qi5BEB?usp=sharing
```


### Relevant log output

```shell
Check failed: d < dims() (0 vs. 0)
Aborted (core dumped)
```
