Fix sync-perm CLI command

[vincbeck]

If you run airflow sync-perm in main you'll get the error:

[2025-03-11T14:37:55.804+0000] {init_appbuilder.py:551} ERROR - 'NoneType' object has no attribute 'permissions'
Traceback (most recent call last):
  File "/opt/airflow/providers/fab/src/airflow/providers/fab/www/extensions/init_appbuilder.py", line 549, in _add_permission
    self.sm.add_permissions_view(baseview.base_permissions, baseview.class_permission_name)
  File "/opt/airflow/providers/fab/src/airflow/providers/fab/auth_manager/security_manager/override.py", line 1120, in add_permissions_view
    self.add_permission_to_role(admin_role, action)
  File "/opt/airflow/providers/fab/src/airflow/providers/fab/auth_manager/security_manager/override.py", line 1704, in add_permission_to_role
    if permission and permission not in role.permissions:
AttributeError: 'NoneType' object has no attribute 'permissions'

This PR fixes this issue.

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