az login --allow-no-subscriptions crashes in tenant selector: 'NoneType' object has no attribute 'get' (personal MSA, no subscriptions) #34252

Describe the bug

az login --allow-no-subscriptions crashes in the interactive tenant/subscription selector for a personal Microsoft account (Gmail-based MSA) that has no Azure subscriptions. Plain az login reports No subscriptions found for <account>. and exits.

The traceback matches #31992 (closed), so this may be a regression or an unhandled case.

Related command

az login --allow-no-subscriptions

Errors

Retrieving tenants and subscriptions for the selection...

[Tenant and subscription selection]

The command failed with an unexpected error. Here is the traceback:
'NoneType' object has no attribute 'get'
Traceback (most recent call last):
  File "...\knack/cli.py", line 233, in invoke
  File "...\azure/cli/core/commands/__init__.py", line 677, in execute
  File "...\azure/cli/core/commands/__init__.py", line 820, in _run_jobs_serially
  File "...\azure/cli/core/commands/__init__.py", line 789, in _run_job
  File "...\azure/cli/core/commands/__init__.py", line 335, in __call__
  File "...\azure/cli/core/commands/command_operation.py", line 120, in handler
  File "...\azure/cli/command_modules/profile/custom.py", line 238, in login
  File "...\azure/cli/command_modules/profile/custom.py", line 128, in _select_and_set_active
  File "...\azure/cli/command_modules/profile/_subscription_selector.py", line 69, in __call__
  File "...\azure/cli/command_modules/profile/_subscription_selector.py", line 98, in _get_tenant_string
AttributeError: 'NoneType' object has no attribute 'get'

Steps to reproduce

1. Use a personal Microsoft account with no Azure subscriptions.
2. Run az login and pick the account. Result: No subscriptions found for <account>.
3. Run az login --allow-no-subscriptions and pick the same account. Result: the crash above.

Expected behavior

Login succeeds with a tenant-level account, or the CLI prints a clear message (for example that the account has no accessible tenant) instead of an unhandled exception. _get_tenant_string should handle a tenant entry with missing info.

Environment

• azure-cli 2.91.0 (azure-cli-core 2.91.0, telemetry 1.1.0), no extensions
• Windows, Windows PowerShell 5.1

Additional context

Use case: publishing a VS Code extension with vsce publish --azure-credential now that Azure DevOps PATs are being retired.