[BUG] sub page of restricted page with "Extend to Subpages" is not indexed

[deschilter]

Describe the bug
When a page is restricted to an fe_group by restricting the parent page and activating the "Extend to Subpages", it won't be indexed.
The indexing request will result in a 404 and the frontendHelper is never called.

This is because no or pageUserGroup is passed in the request.
It is only passed if the current page is restricted: PageIndexer.php#L297
In that case the FrontendGroupsModifier would grant access to the page, but without a userGroup or a pageUserGroup, it won't.

To Reproduce
Steps to reproduce the behavior:

1. Create a page called parent and restrict it to any fe_group
2. Check Extend to Subpages for the page parent
3. Create a subpage for the page parent called child
4. Index the pages

Expected behavior
Both pages, parent and child, should be correctly indexed.
Currently only the parent is indexed and the child results in an error.

Used versions (please complete the following information):

• TYPO3 Version: 12.4.11
• EXT:solr Version: 12.0.2
• Used Apache Solr Version: typo3solr/ext-solr:latest
• PHP Version: 8.1.26

[deschilter]

It seems this was introduced by this change and should therefore only affect v12

[dkd-kaehm]

It seems this was introduced by this change and should therefore only affect v12

@deschilter There are 13 files changed, which part of change exactly?

Is #3926 related? Could you try if that fixes the issue?

[deschilter]

The part which checks if the FrontendGroupsModifier should be applied.
a6168bc#diff-bf28763c35325e20091cdc41e71675d16a1f04fb2dbf94f7adb0b1d0f61abaf0R44

I tested #3926 and it does not solve this issue.