bug#18263: Wrong type argument: markerp, nil

[Glenn Morris]

Glenn Morris wrote:

> The short answer is that replace-regexp removes the text properties that
> occur-edit-mode relies on.

I guess no-one expected you to edit the start of the line (the line
number prefix that is not part of the actual source buffer).
Maybe it should be read-only like the header line is
(though then you would still get an error trying to replace-regexp).
Or displayed using an overlay?