Make Urban Rights disable downgrading an Urban location (cheesing PI)

[Siz]

I think it's a really silly thing to make a built-up Town or larger delete all its buildings just so you can save on Political Influence - when it's downgraded to Rural it loses the Urban Rights, thus you save 20+ PI.

Please make an Urban Right disable downgrading it to Rural rank.

[SilverFish]

20PI is not worth the gold a city/town cost if it have anything in it