Editor was attempting to delete non-existent chars which is UB. Fixed by
checking before deleting. Also fixed was a problem created by having to
press enter to change the search string which advanced the selection to
the first match. In the next step one would expect that pressing enter
on the replace field would replace the selected item but was replacing
the item found after he first.
This was fixed by always replacing the current selection first. If the
replacement is the same as the searched term then replacing won't
advance the cursor, but if they are different then the current match
will no longer exist so it would search fora new one.
