Reproducing steps:
set interfaces wireless wlan0 address 'dhcp'
set interfaces wireless wlan0 disable
set interfaces wireless wlan0 security wpa passphrase 'XXXXX'
set interfaces wireless wlan0 ssid 'test'
set interfaces wireless wlan0 type 'station'
vyos@WIFI# sudo ip addr show dev wlan0
5: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
link/ether cc:cc:02:84:cc:cc brd ff:ff:ff:ff:ff:ff
inet 192.168.0.104/24 brd 192.168.0.255 scope global dynamic wlan0
valid_lft 172535sec preferred_lft 172535sec
inet6 fecc::821f:2ff:fecc:cccc/64 scope link
valid_lft forever preferred_lft forever