send-email: ignore trailing whitespace in mailrc alias file

The regex for parsing mailrc considers everything after the second whitespace to be the email address, up to the end of the line. We have to include whitespace there, because you may have multiple space-separated addresses, each with their own internal quoting. But if there is trailing whitespace, we include that, too. This confuses quotewords() when we try to split the individual addresses, and we end up storing "undef" in our alias list. Later parts of the code then access that, generating perl warnings. Let's tweak our regex to throw away any trailing whitespace on each line. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>