If SSL verification is enabled in git send-email, we could attempt to call a
method on an undefined value if the verification failed, since $smtp would end
up being undef. Look up the error string in a way that will produce a helpful
error message and not cause further errors.
Signed-off-by: Brian M. Carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>