[Exim] application bug - it's back!

On RH9 Linux, I previously reported the dreaded "application bug" error
message. Supposedly this was fixed in 4.14. Now I'm running 4.22, but the
message seems to be back:

Sep 11 11:49:33 rpppc1 kernel: application bug: exim(24615) has SIGCHLD set to
SIG_IGN but calls wait().
Sep 11 11:49:33 rpppc1 kernel: (see the NOTES section of 'man 2 wait').
Workaround activated.