Some addresses are passed twice to unique_email_list() and invalid addresses
may be reported twice per send_message. Now we warn about them earlier
and we also remove invalid addresses.
This also removes using of undefined values for string comparison
for invalid addresses in cc list processing.
Signed-off-by: Krzysztof Mazur <krzysiek@podlesie.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>