[PT2] - Add check for stack (#108012)
Summary:
Add check for `guard.stack` which was causing exceptions like:
```
toch._dynamo.exc.InternalTorchDynamoError: 'NoneType' object has no attribute 'format'
```
Test Plan: contbuild & OSS CI
Differential Revision: D48709458
Pull Request resolved: https://github.com/pytorch/pytorch/pull/108012
Approved by: https://github.com/anijain2305
