Submenus don't move when mouse moves to different menu item.

[jdalbey]

Expected behavior: Click on a menu item (e.g., 'File') and the submenu expands. Move the mouse to the second menu item (e.g. 'Edit'). The submenu for the File should close and the submenu for Edit should open. This should happen seamlessly, appearing as though the submenu simply shifts to the right. (This is how PyQt menu bar functions). Actual behavior: The File submenu remains open. In this screenshot, the mouse has moved to the Edit menu but the File submenu is still present.