- shellcmd completion is VERY slow on both WSL and Windows, e.g. `term
something` or `!something` might take ~10 seconds to show first
results. Do not complete it there.
- revert previous change to not complete on whitespace, do not complete
on *empty* lines instead.
closes: #18568
Signed-off-by: Maxim Kim <habamax@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>