33563: Completion/Base/Core/_main_complete, Src/Zle/complist.c: fix thinko in status message for INT/QUIT signals; check errflag in output loops

Two semi-related patches for keyboard interrupt handling in completion,
most importantly so that unexpectedly long completion listings can be
interrupted.
33566: quash null pointer constant compiler warning
Merge branch 'master' of git://git.code.sf.net/p/zsh/code

Conflicts:
	ChangeLog