Filtering Events in wagtailCRX Fails

#### Describe the bug
Filtering Events in wagtailCRX Fails

#### Steps to reproduce
Steps to reproduce the behavior:
1. Create a classifier and populate it with classifier terms (In my case Deejee populated with the names of dj's)
2. Create an events landing page. and check under Filter child pages by: the classifier(s) you like to filter on. (in my case Deejee)
3. Add a few events and classify the events with different classifier terms. (in my case each event is classified with the Dejee>name_of_deejee)
4. Open the events landing page live view
5. Go to Filter selector and choice the classifier term you like to filter on and click Filter
6.In the log get the error:

"Tried to filter by ClassifierTerm in PageListBlock, but .get_index_children() did not return a queryset or is not a queryset of CoderedPage models.

7. I expected to see only the get the events with the selected dj but it gives back all events.

#### Additional context
I tried the same with the article landing page and there it works fine.

Django version 5.2.6
Wagtail version 7.71
Codered 6.0.0

Reproduce the issue with the listed Django, Wagtail, and CodeRed versions, then inspect the event landing page filtering path and its get_index_children() behavior. Compare it with the article landing page, where filtering works; done means selecting a classifier term shows only matching events without the logged error.

Written by the indexing model from the issue text.