[account] Guard deserializer against None headers during login/account discovery

[Copilot]

This checklist is used to make sure that common guidelines for a pull request are followed.

Related command

az login (failure surfaced while account/tenant/subscription retrieval runs post-authentication on broker-enabled Windows environments)

General Guidelines

• Have you run azdev style <YOUR_EXT> locally? (pip install azdev required)

• Have you run python scripts/ci/test_index.py -q locally? (azdev required; see .azure-pipelines/templates/azdev_setup.yml for the install command until azdev==0.2.11b1 is on PyPI)

• My extension version conforms to the Extension version schema

• Issue summary

  • az login could fail with argument of type 'NoneType' is not iterable when downstream account-discovery response headers are unexpectedly None in broker-enabled flows.

• Change made

  • Added a null guard in account extension vendored subscription deserialization so content-type detection does not iterate on None.
  • Behavior now falls back to default JSON handling when headers are absent, instead of throwing a TypeError.

• Regression coverage

  • Added a focused unit test validating deserialize_from_http_generics(..., headers=None) is handled safely.

# before
if "content-type" in headers:

# after
if headers and "content-type" in headers:

For new extensions:

• My extension description/summary conforms to the Extension Summary Guidelines.

About Extension Publish

There is a pipeline to automatically build, upload and publish extension wheels.
Once your pull request is merged into main branch, a new pull request will be created to update src/index.json automatically.
You only need to update the version information in file setup.py and historical information in file HISTORY.rst in your PR but do not modify src/index.json.

[azure-client-tools-bot-prd]

️✔️Azure CLI Extensions Breaking Change Test

️✔️Non Breaking Changes

[azure-client-tools-bot-prd]

Hi @copilot,
Please write the description of changes which can be perceived by customers into HISTORY.rst.
If you want to release a new extension version, please update the version in setup.py as well.

[yonzhan]

account