I looked at the diff file you proposed very thoroughly. And I must conclude that your fix is nothing more but a bullshit. The only thing your fix does - it protects PastRateActualSeconds varibale in a way that it is always >= 1 (second). Old code assumed it was always >= 0. You probably cared about PastRateAdjustmentRatio variable which is equal to 1 if PastRateActualSeconds happens to be 0. But the point is that it never happens. KGW takes at least PastBlocksMin and at most PastBlocksMax blocks into the calculation. You will never have PastRateActualSeconds == 0 except for the case if your blockchain has only one block.