qt: fix sub-grid views in home and browse pages going out of bounds
It appears that d4c114ea revealed this bug in ExpandGridView
.
I have not observed this before, because it was still dormant in
the home page without b1f3e4ef, which was added in the last minute.
Nevertheless, this should have been observable in the browse
page, but for some reason I have not observed it there either.
Regression since !7023 (merged).