[nrf fromtree] runners: jlink: Fix NoneType object error#2375

nordicjm merged 2 commits intonrfconnect:mainnrfconnect/sdk-zephyr:mainfrom

nordic-krch:ncs/jlink_fixnordic-krch/fw-nrfconnect-zephyr:ncs/jlink_fixCopy head branch name to clipboard