strlist: allow storing NULL
strlist: allow storing NULL

rabbitt/libusual,markokr/libusual,mgjv/libusual,rabbitt/libusual,mgjv/libusual,mgjv/libusual,rabbitt/libusual,mgjv/libusual,ifduyue/libusual,markokr/libusual,ifduyue/libusual,ifduyue/libusual,ifduyue/libusual,markokr/libusual,rabbitt/libusual,markokr/libusual