Pressing other mouse button during tree drag should cancel

In Opus 9 list views, as in Explorer and most Windows apps, pressing any other mouse button during a drag cancels the drag.

For example, start dragging a file in an Opus list with the left button, then press the middle or right button. The drag is immediately canceled.

This doesn't work in Opus tree views. Nothing happens when you press the other mouse button.

I know you can cancel the drag with the Escape key, but canceling by pushing an extra button is especially convenient. It would be nice to make this work in the tree views.

Thanks!