Null pointer dereference in lmhlo_to_cpu_runtime.cc
@mihaimaruseac  

https://github.com/tensorflow/tensorflow/blob/c1169a1ba98e1c5d0874cd44ffeb605bfd1cefba/tensorflow/compiler/xla/mlir/backends/cpu/transforms/lmhlo_to_cpu_runtime.cc#L145-L149 @SweetVishnya Thanks for the PR.

@PaDarochek The issue will be closed once the PR is merged.

Thanks. Are you satisfied with the resolution of your issue?
<a href="https://docs.google.com/forms/d/e/1FAIpQLSfaP12TRhd9xSxjXZjcZFNXPGk4kc1-qMdv3gc6bEP90vY1ew/viewform?entry.85265664=Yes&entry.2137816233=https://github.com/tensorflow/tensorflow/issues/60223">Yes</a>
<a href="https://docs.google.com/forms/d/e/1FAIpQLSfaP12TRhd9xSxjXZjcZFNXPGk4kc1-qMdv3gc6bEP90vY1ew/viewform?entry.85265664=No&entry.2137816233=https://github.com/tensorflow/tensorflow/issues/60223">No</a>

<details><summary>Click to expand!</summary> 
 
 ### Issue Type

Bug

### Have you reproduced the bug with TF nightly?

Yes

### Source

source

### Tensorflow Version

tf 2.12

### Custom Code

No

### OS Platform and Distribution

_No response_

### Mobile device

_No response_

### Python version

_No response_

### Bazel version

_No response_

### GCC/Compiler version

_No response_

### CUDA/cuDNN version

_No response_

### GPU model and memory

_No response_

### Current Behaviour?

```shell
Variable `dict` may be `nullptr` and is dereferenced on line 149 in `tensorflow/compiler/xla/mlir/backends/cpu/transforms/lmhlo_to_cpu_runtime.cc`.  

`dict` is initialized on line 146 and may equal `nullptr`. Then it is dereferenced on line 149.  
```


### Standalone code to reproduce the issue

```shell
Bug was found by Svace static analysis tool.
```


### Relevant log output

_No response_</details>