QtQuickControls 2 Menu should not popup if it becomes visible under mouse cursor

If a QtQuickControls 2 Menu becomes visible at the location of the mouse cursor, it automatically opens. This is undesirable because it interferes with using menus with keyboard commands. The menu should open only if the mouse hovers over it but not if it accidentally opens below the mouse cursor.

To reproduce this bug, run the attached Main.qml on a desktop (where Menu.cascade is true by default) and perform the following steps:

1. Open Menu and move the mouse above Submenu. The submenu should now open automatically.
2. Don't move the mouse anymore but close the menu by pressing escape twice.
3. Open Menu with the keyboard by pressing Alt-M. Now Submenu becomes visible under the mouse cursor and immediately opens. This is undesirable because the user might first have wanted to select between the items in Menu (Submenu and Item 1) with further keyboard commands.