Is there a key command to deselect all tracks?

I'm new to this program. Just started using PT 10 HD. If you have all channels in mixer selected, how do you de-select or un-select them.

I figured out you can de-select a range of tracks by clicking on an unselected one. But what if there's no un-selected track to click on?

I've been creating a new track just to de-select all the others. Can someone tell me if there's a better way to do this?