fixed sendmail error while sending emails to the member who has no email address (fixes #421)
fixed sendmail error while sending emails to the member who has no email address (fixes #421)

ShinichiU/AuthFramework,openpne/OpenPNE3,ShinichiU/OpenPNE3_with_webInstaller,upsilon/travis-test,nishizoe/OpenPNE3,upsilon/OpenPNE3,ShinichiU/OpenPNE3,nise-nabe/ppcon-sns,openpne/OpenPNE3,C-nakajima/OpenPNE3,isaosano/OpenPNE3,tejima/testravis,C-nakajima/OpenPNE3,isaosano/OpenPNE3,tejima/testravis,nise-nabe/ppcon-sns,C-nakajima/OpenPNE3,ShinichiU/OpenPNE3,ShinichiU/OpenPNE3,tejima/OP3PKG,kashiwasan/symfony-advanced,upsilon/OpenPNE3,kashiwasan/symfony-advanced,upsilon/travis-test,ShinichiU/OpenPNE3,tejimaya/OpenPNE3,nishizoe/OpenPNE3,C-nakajima/OpenPNE3,openpne/OpenPNE3,tejimaya/OpenPNE3,isaosano/OpenPNE3,isaosano/OpenPNE3,ShinichiU/OpenPNE3_with_webInstaller,tejima/OP3PKG,balibali/KakiageSNS,openpne/OpenPNE3,ShinichiU/AuthFramework,ShinichiU/AuthFramework,balibali/KakiageSNS,tejima/testravis