title: Is it possible to deselect in a QTreeView by clicking off an item?
body: <p>I'd like to be able to deselect items in my QTreeView by clicking in a part of the QTreeView with no items in, but I can't seem to find anyway of doing this. I'd intercept a click that's not on an item, but the QTreeView doesn't have a <code>clicked</code> signal, so I can't work out how to do this.</p>