Submenu clickable when closed

[hw-df]

After clicking on a submenu item, the item stays clickable as long as you hover over it´s position.

Testcase: https://jsfiddle.net/k3hmdo6n/

What to do:
click on "Add a marker" in "Some actions" submenu. Click on the same position (don't move mouse) after contextmenu has closed.

What I expect:
Nothing should happen. No new marker should be added.

What happens:
Another marker was added. See console output.

After clicking a submenu item the contextmenu closes by hiding itself in CSS (opacity: 0; visibility hidden;). But if the mouse stays in the contextmenu area a hover rule prevents the "visibility:hidden" for the submenu. It is invisible due to the opacity of the parent, but still clickable. Opacity cannot be overridden by a child.

I could provide a solution via PR.