anchor.diff:    Result := -1;
     HTS := [];
     for B := Low(HouseIndexToType) to High(HouseIndexToType) do
  -    if B in aHouseTypes then
  +    if (B in aHouseTypes) and (HouseIndexToType[B] <> ht_None) then
         HTS := HTS + [HouseIndexToType[B]];
   
     if InRange(aPlayer, 0, gHands.Count - 1) and (gHands[aPlayer].Enabled)
  
positive.code:   Result := False;
    //Verify all input parameters
    if InRange(aPlayer, 0, gHands.Count - 1) and (gHands[aPlayer].Enabled)
    and (aHouseType in [Low(HouseIndexToType)..High(HouseIndexToType)])
    and gTerrain.TileInMapCoords(X,Y) then
    begin
      if gHands[aPlayer].CanAddHousePlan(KMPoint(X, Y), HouseIndexToType[aHouseType]) then
  
negative.code: function TKMScriptStates.HouseTypeToOccupantType(aHouseType: Integer): Integer;
  begin
    Result := -1;
    if HouseTypeValid(aHouseType) then
    begin
      Result := UnitTypeToIndex[gResource.HouseDat[HouseIndexToType[aHouseType]].OwnerType];
    end
  