Library grid view: wrong page and item heights

[gwuen]

The height of the CarouselGridView on library pages like "Library" and "Artists" does not seem to be calculated correctly.

When reducing the window's width, fewer columns are displayed leading to the grid items needing more vertical space. But the GridView's height appears to be static, causing a huge blank space (of more than three quarters of the page) when showing five columns up to the last item being cut off when just showing one column.

The other bug is the individual grid items (GtkListItemWidget) growing in size vertically every time more items are loaded (by clicking on "Load More"), visible as a blank space under each item's caption. At least the GridViews's height also gets bigger when loading more items, but it's still not the correct height.

The latter bug I only observed on the "Library" page, but I figure it would be the same on the other pages if the "Load More" button was functional there (see #156).

I could reproduce neither bug on the artist album page (which also uses the CarouselGridView), so this may have something to do with the (missing) "Load More" button (see vixalien/muse#11).