Cannot remove attribute

[ukasiu]

E.g.
after changing from:

      - action: drop
        disabled: "false"
        chain: forward
        src-address-list: ABC
        comment: drop from ABC
        dst-address: 8.8.8.8
        place-before: 12

to

      - action: drop
        disabled: "false"
        chain: forward
        src-address-list: ABC
        comment: drop from ABC
        place-before: 12

dst-address is still set.