Avoid _zip_memdup of NULL.
Avoid _zip_memdup of NULL.

projedi/libzip,JanX2/libzip-git,det/libzip,det/libzip,cysp/libzip,JanX2/libzip-git,projedi/libzip,projedi/libzip,cysp/libzip,det/libzip,cysp/libzip,det/libzip,projedi/libzip,cysp/libzip