assimilation and ice thickness

[clem]

Context

In assimilation there is an attempt to change ice thickness but hm_i is a diagnostic and is not used in the ice code. I wonder whether the authors of this part really wanted to change the thickness or were just making a test. It concerns both the trunk and 4.0-HEAD

            ! Nudge sea ice depth to bring it up to a required minimum depth
            WHERE( zseaicendg(:,:) > 0.0_wp .AND. hm_i(:,:) < zhicifmin )
               zhicifinc(:,:) = zhicifmin - hm_i(:,:)
            ELSEWHERE
               zhicifinc(:,:) = 0.0_wp
            END WHERE
            !
            ! nudge ice depth
            hm_i (:,:) = hm_i (:,:) + zhicifinc(:,:)