Sets the #GtkPopover that will be popped up when the menu_button is clicked,
or null to dissociate any existing popover and disable the button.
If #GtkMenuButton:menu-model or #GtkMenuButton:popup are set, those objects
are dissociated from the menu_button, and those properties are set to null.
Sets the #GtkPopover that will be popped up when the menu_button is clicked, or null to dissociate any existing popover and disable the button.
If #GtkMenuButton:menu-model or #GtkMenuButton:popup are set, those objects are dissociated from the menu_button, and those properties are set to null.