Visualization click during hover causes "dangling selections"

[alancleary]

Most visualization elements in GCV have a hover effect, that is, hovering over an element causes other elements (possibly in other visualizations) to be grayed out or highlighted, depending on their relationship to the element being hovered. This effect is reversed when the element being hovered is unhovered (a mouseout event). However, some elements also have a click event that opens a new window that covers them. This prevents the unhover event from occurring causing "dangling selections" - a highlighted (selected) other element that was never deselected. These artifacts are visible when you hover over another element and they appear as highlighted even though they're not related to the highlighted element. This is a bug. Fix it!