Fix crashes that won't happen in regular usage:
- If you open the menu with an empty menu-data and use keybindings
- If you open the menu with menu-data only containing hidden items
- If you invoke script-message-to context_menu select with the menu
closed
This implements a ASS context menu to be used on platforms other than
Windows.
The select script message will allow selecting an item with a single
click when releasing a mouse button, like in native context menus. This
is mainly useful to cycle pause with one click.
Guido Cella