Fix CRs gor paragraphs with empty br

[Elblinator]

Describe the bug
If a motion has <p> <br> text</p>

How to Reproduce

1. Create a motion with the following text

<p>
<br>first</p>
<p>
<br>secoond</p>
<p>third</p>

2. create a CR on line 1 and add a new character
3. The motion will look at like the following
   

Expected behavior
Line 1 should not appear two times (the empty line should not be there)
Below the "first fg" is a lot of space which should not be there

(see line 3)

[Elblinator]

this could be connected to #5164