A minor simplification for List manipulation
Fix one place that was using lfirst(list_head(list)) by using linitial(list)
instead. They are equivalent but the latter is simpler. We did the same in
9d299a49.
Author: Richard Guo <guofenglinux@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAMbWs49dJnpezDQDDxCPKq7+=_3NyqLqGqnhqCjd+dYe4MS15w@mail.gmail.com