Farm using fallowing is punished for lack of crops rotation

Issue description

It seems that planting potatoes alternately with fallowing land doesn't count as rotation of crops. Thus farm is penalized with 50% faster fertility loss.

Expected behavior

Leaving land fallow is traditional technique of rotating crops, so no penalty.

Reproduction steps

1. Build a farm, set slots to potatoes and "no crops"
2. Wait ~7 months to second cycle
3. Note: Fertility loss has bold font and is raised about 50%

Game version

v0.4.11

This actually works as intended. Crops rotation only works when you actually rotate different crops. Empty field does not count as a different crop.

Oh. I thought it was kind of water-saving manure.