use empty string to clear member cache (fixes #3416)
use empty string to clear member cache (fixes #3416)

ShinichiU/OpenPNE3,isaosano/OpenPNE3,C-nakajima/OpenPNE3,ShinichiU/OpenPNE3,C-nakajima/OpenPNE3,C-nakajima/OpenPNE3,nishizoe/OpenPNE3,isaosano/OpenPNE3,isaosano/OpenPNE3,isaosano/OpenPNE3,C-nakajima/OpenPNE3,ShinichiU/OpenPNE3,ShinichiU/OpenPNE3,nishizoe/OpenPNE3