Mail: added a check for the number of arguments in MAIL/RCPT.
Mail: added a check for the number of arguments in MAIL/RCPT.

Missed during introduction of the SMTP pipelining support (04e43d03e153,
1.5.6).  Previously, the check wasn't needed as s->buffer was used directly
and the number of arguments didn't matter.

Reported by Svyatoslav Nikolsky.

hy0kl/nginx,firebase/nginx,firebase/nginx,firebase/nginx,hy0kl/nginx,firebase/nginx,hy0kl/nginx