patch 9.1.1381: completion: cannot return to original text

patch 9.1.1381: completion: cannot return to original text

Problem:  Cannot return to the original text after selecting the next
          item when the currently selected item is the last one.
Solution: When continuing to move down past the last item, locate the
          original completion at the head/tail nodes of the completed
          linked list (glepnir).

closes: #17300

Signed-off-by: glepnir <glephunter@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>