"Album covers" view in main panel. "Show tracks for the selected albums" is ticked, with the track display style set to "directly under the selected album".
Clicking selects an album. Ctrl + clicking selects multiple albums. Ctrl + clicking unselects albums, but only until the last one. You don't seem to be able to unselect that single album in any other way than clicking on some selection in the left main panel.
However, if you have set the tracks of selected album(s) to be shown to the right or under the main panel, then ctrl + clicking does allow unselecting that last album.
I tried googling for a solution, but about the only one I found talked about using the "Reset search and browse filters" hotkey, but that does nothing when using the "Album covers" view.