Problem: crash with NFA regex engine when searching for composing chars
(SuyueGuo)
Solution: When there is no composing character, break out of the loop
and check that out1 state is not null
fixes: vim/vim#15583c3a02d78bd
Test uses DBCS 'encoding', which is N/A.
Co-authored-by: Christian Brabandt <cb@256bit.org>
