A recent update to system recipe (systemd_229.bb) resulted in do_install to fail. The following are the changes:

USERADD_PACKAGES = "${PN} ${PN}-extra-utils"
USERADD_PARAM_${PN} += "${@bb.utils.contains('PACKAGECONFIG', 'microhttpd', '--system -d / -M --shell /bin/nologin systemd-journal-gateway;', '', d)}"
USERADD_PARAM_${PN} += "${@bb.utils.contains('PACKAGECONFIG', 'microhttpd', '--system -d / -M --shell /bin/nologin systemd-journal-remote;', '', d)}"
USERADD_PARAM_${PN} += "${@bb.utils.contains('PACKAGECONFIG', 'journal-upload', '--system -d / -M --shell /bin/nologin systemd-journal-upload;', '', d)}"
USERADD_PARAM_${PN} += "${@bb.utils.contains('PACKAGECONFIG', 'timesyncd', '--system -d / -M --shell /bin/nologin systemd-timesync;', '', d)}"
USERADD_PARAM_${PN} += "${@bb.utils.contains('PACKAGECONFIG', 'networkd', '--system -d / -M --shell /bin/nologin systemd-network;', '', d)}"
USERADD_PARAM_${PN} += "${@bb.utils.contains('PACKAGECONFIG', 'coredump', '--system -d / -M --shell /bin/nologin systemd-coredump;', '', d)}"
USERADD_PARAM_${PN} += "${@bb.utils.contains('PACKAGECONFIG', 'resolved', '--system -d / -M --shell /bin/nologin systemd-resolve;', '', d)}"
GROUPADD_PARAM_${PN} = "-r lock; -r systemd-journal"
USERADD_PARAM_${PN}-extra-utils += "--system -d / -M --shell /bin/nologin systemd-bus-proxy;"


To simplify things, lets shorten the above settings to:

USERADD_PACKAGES = "${PN}" "${PN}-a"
USERADD_PARAM_${PN} += x; 
USERADD_PARAM_${PN} += y;
USERADD_PARAM_${PN}-a = z;

As a result of parsing these settings by get_all_cmd_parse() in meta/classes/useradd.bbclass, this turns out to be:

x; y; ; z;

"; ".join(params) introduces an additional semicolon in the list. As a result, perform_useradd runs with empty argument listand causes do_install() to fail.