Odd BGridLayout behavior

[anevilyak]

Since ​http://cgit.haiku-os.org/haiku/commit/src?id=7910d8b89cc2285eba6efc8c16475dd06617bc8b 's changes to BCheckBox's preferred width, some odd behavior has been visible in the Backgrounds preflet. The latter uses a grid layout with two BMenuFields and a BCheckBox, all in separate rows, where rows 0 and 1 each have two layout items for the label + menu spread across columns 0 and 1, and row 2 has just the BCheckBox in column 1. Picking the Image menu field in row 0 and picking "None" for the choice of image causes it and its respective label to jump to the right. Picking another longer name brings it back to normal. This behavior makes no sense though, since the checkbox isn't even in the same row, and one would expect any influence of the checkbox to affect all of column 1, not just that single row.