Dragging a box select and then pressing alt keeps box on screen

[BrentFarris]

1. Open a project
2. In 3D stage view click and drag to create a select box (keep mouse down)
3. Press alt to begin rotating the camera

Notice the box is stuck on screen until you click again

Expected behavior would be to clear the box selection when the camera starts any actions (orbit, pan, zoom, fly).

[BrentFarris]

Oh, woops. I didn't notice there was already a commit from majiayu000 that I could pull in for this ticket and we literally have an identical fix. I didn't even know I could click on those and create a PR from someone else's commits that are referenced here directly on GitHub; neat! I'll remember that for next time.