patch 9.1.0651: ex: trailing dot is optional for :g and :insert/:append

patch 9.1.0651: ex: trailing dot is optional for :g and :insert/:append

Problem:  ex: trailing dot is optional for :g and :insert/:append
Solution: don't break out early, when the next command is empty.
          (Mohamed Akram)

The terminating period is optional for the last command in a global
command list.

closes: #15407

Signed-off-by: Mohamed Akram <mohd.akram@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>