Fix post processing for VIJHF datalayouts

[charleskawczynski]

The issue seems to be that slab for VIJHF returns view(parent(data), :, :, h, :), which we try to index in rmatmul1(M, in_slab, i, j), leading to scalar indexing. We may be able to simply wrap that call in an SArray, but I'd like to look at this more carefully.