Productivity of the Atlantean farm does not drop to 0 when it does not work

[wl-zocker]

Observed in r6989 and only (easily) reproducible while bug 1332452 is not yet fixed.

1) Start a new game as Atlanteans. Build a farm and a blackroot farm.
2) They will both plant their fields. Because of said bug, the fields will not grow, so that after some time, the farmers do not have any space left to plant new fields.
3) The productivity of the blackroot farmer drops to 0 because he cannot do anything (neither plant nor harvest). The productivity of the corn farm only drops to 35%, although the corn farmer does not work anything neither.

You can also block as many fields as possible near the farm by immovables in the editor. The farm will then place two fields (productivity 10%, I think). Afterwards, the productivity raises to 35%.
The Barbarian and Imperial farm behave like the blackroot farm, i.e. their productivity drops to 0, as expected.

I do not know whether this difference is visible in normal games, but it might lead to wrong conclusions in some cases.

[SirVer (sirver)]

Fixed in r7068.

[GunChleoc (gunchleoc)]

Fixed in build19-rc1.