Errors when working with DevOps permissions

When working with az devops security permissions, multiple commands generate the below error output. This happens with:

az devops security permission list --id $namespaceId --subject $subject
az devops security permission reset-all --id $namespaceId --subject $subject --token $token

This happens when using a group descriptor (i'm using the group ID that starts with vssgp.) and a UPN. The token, subject and namespace ID seem to be correct because az devops security permission update does work with the same values.

### **This is autogenerated. Please review and update as needed.**

## Describe the bug

**Command Name**
`az devops security permission list
Extension Name: azure-devops. Version: 0.25.0.`

**Errors:**
```
The command failed with an unexpected error. Here is the traceback:
'NoneType' object has no attribute 'descriptor'
Traceback (most recent call last):
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\knack/cli.py", line 231, in invoke
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 658, in execute
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 721, in _run_jobs_serially
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 713, in _run_job
File "C:\Users\jholtkamp\.azure\cliextensions\azure-devops\azext_devops\dev\common\exception_handler.py", line 31, in azure_devops_exception_handler
reraise(*sys.exc_info())
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\six.py", line 703, in reraise
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 692, in _run_job
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 328, in __call__
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/command_operation.py", line 121, in handler
File "C:\Users\jholtkamp\.azure\cliextensions\azure-devops\azext_devops\dev\team\security_permission.py", line 45, in list_tokens
subject = _resolve_subject_as_identity_descriptor(subject, organization)
File "C:\Users\jholtkamp\.azure\cliextensions\azure-devops\azext_devops\dev\team\security_permission.py", line 198, in _resolve_subject_as_identity_descriptor
subject = get_identity_descriptor_from_subject_descriptor(subject_descriptor=subject, organization=organization)
File "C:\Users\jholtkamp\.azure\cliextensions\azure-devops\azext_devops\dev\common\identities.py", line 136, in get_identity_descriptor_from_subject_descriptor
return identities[0].descriptor
AttributeError: 'NoneType' object has no attribute 'descriptor'

```

## To Reproduce:
Steps to reproduce the behavior. Note that argument values have been redacted, as they may contain sensitive information.

- _Put any pre-requisite steps here..._
- `az devops security permission list --id {namespaceId} --subject {subjectDescriptor}`

## Expected Behavior

## Environment Summary
```
Windows-10-10.0.19041-SP0
Python 3.8.9
Installer: MSI

azure-cli 2.34.1 *

Extensions:
account 0.2.2
azure-devops 0.25.0

Dependencies:
msal 1.16.0
azure-mgmt-resource 20.0.0
```
## Additional Context