This is a response to the message of Lars. Apparently, we get the same backtrace.
```
Debugger entered--Lisp error: (error "Negative repetition argument -1")
self-insert-command(-1)
newline(-1)
open-line(-1)
eval((open-line -1) t)
eval-_expression_((open-line -1) nil nil 127)
funcall-interactively(eval-_expression_ (open-line -1) nil nil 127)
call-interactively(eval-_expression_ nil nil)
command-execute(eval-_expression_)
```
This is what C-h f open-line RET shows
```
open-line is an interactive compiled Lisp function in ‘simple.el’.
It is bound to C-o, <insertline>.
(open-line N)
Probably introduced at or before Emacs version 19.29.
Insert a newline and leave point before it.
If there is a fill prefix and/or a ‘left-margin’, insert them on
the new line if the line would have been blank.
With arg N, insert N newlines.
```