Fix display of amendment from amendment

[Elblinator]

Describe the bug
If an amendment is created on an amendment then inserted text is sometimes not indicated as new text

How to Reproduce

1. Activate the setting "Allow amendment of amendments"
2. Create a motion
3. Create an amendment which creates a new line
4. In the amendment view: create a new amendment
5. While selecting which lines you want to edit the completely new line is not indicated as such and the paragraph which has a new line there are no numbers behind the line indicator

The amendment:

Creation mask:

Expected behavior:

• New lines should be displayed as a inserted line
• The Indicated line numbers should be the same as they are in the motion