when splitRows with 3 splits, with even number of parent rows, the last split is not expanding by 1 row

[goblinfactory]

given a screen with 10 rows
when using splitRows with 3 even splits
then the last split (bottom one) should expand by 1 row so that the screen is fully split with no gaps.
// currently the splits end up as 3, 3 and 3 when we need it to be 3, 3 and 4.