./rock64_write_spi_flash.sh fails

[yanagawa3]

Hi
I am newbie for rockpro64.

I have installed bionic-lxde-rockpro64-0.7.9-1067-arm64 into MicroSD.
It's working fine.

Then I want to have dual boot environment.

When I execute /usr/local/sbin/rock64_write_spi_flash.sh, not successful.

"line22: exit: Unknown package installed.: numeric argument required"

Am I something missing ?
Any help appreciated.

Rockpro64 V2.1