### Steps to reproduce

1. Create a series occurrence

2. Leave it empty

3. From the meetings tab of a WP, try to add it to that occurrence

4. Observe the options available in the section selector


### What is the buggy behavior?

* It appears as if you can only add the WP to the "Series backlog"

* In reality, leaving the selector blank also allows you to add it to the main meeting body, but this is not easy to know

* This option appears in the selector options as "Untitled section" if there already is an agenda item in the meeting, but not when the meeting is empty


### What is the expected behavior?

1. Add the default section as an explicit option that can be selected

2. It has a name that makes sense


### Screenshots and other files

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