Misclicking when attempting to create a range selection causes the current selection to be lost
To reproduce: Select a note or a bar, then shift-click in empty space.
Expected behaviour: If the user is shift-clicking while they have an existing selection, it can be assumed that they're attempting to create a range selection. If they're shift-clicking empty space, it's probably a misclick (e.g. slightly missing a note which is on a ledger line). Therefore, the existing selection should be preserved, so that the user can try again.
Observed behaviour: The user's current selection is dismissed. This means that, in order to create the range selection as intended, they need to start again from the beginning.