BCardLayout with nested layouts does not work

[pulkomandy]

Consider something like this:

BCardLayout* layout = ...;
BLayoutBuilder::Card<>(layout)
    .AddGroup(B_HORIZONTAL)
    .End()
    .AddGroup(B_HORIZONTAL)
        .Add(new BStringView("page 2", "Page 2"))
    .End()
    .SetVisibleItem((int32)0)
.End();

Expected result: the "page 2" string view is not visible, we should be in card 0

Actual result: this does not work.

Workaround: after making the second page explicitly visible and then hidden again, it works. It's just the initial visiblity setting that's broken.