Edit whole motion text amendment parent not loaded

[bastianjoel]

Describe the bug
Motion text is not loaded when creating amendments in "Edit whole motion text" mode.

How to Reproduce
Steps to reproduce the behavior:

1. Change setting Meetings -> How to create new amendments -> Edit whole motion text
2. Navigate to a motion
3. Press the add amendment button
4. Reload

[bastianjoel]

Note that this is not reliably reproducible anymore.

Also now instead of the motion text not being displayed the whole motion form is not displayed as described here: #4024 (review)

[Elblinator]

This is still an Issue: