Pull Request resolves #46944 .

• I read the Generative AI policy and my contribution is either not created with the help of AI or is compatible with the policy and GNU/GPL 2 or later.

Summary of Changes

Before this PR you cannot disable a parent template (in the extension manager) eg Cassiopeia if there is a child template even if the child template is disabled

Testing Instructions

Install any template and make that templates style the default
In extension manager filter by templates and

1. disable cassiopeia_extended
2. disable cassiopeia
3. disable the new template you installed
4. enable cassiopeia_extended

Actual result BEFORE applying this Pull Request

1. Extension disabled.
2. Disabling the parent template is not permitted.
3. Disabling the default template is not permitted.

Expected result AFTER applying this Pull Request

1. Extension disabled.
2. Extension disabled
3. Disabling the default template is not permitted.
4. Enabling a child template when its parent is disabled is not permitted.

Link to documentations

Please select:

• Documentation link for guide.joomla.org:

• No documentation changes for guide.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed