Removed Context::default_window_icon_mut and Context::tray_icon_mut, use Context::set_default_window_icon and Context::set_tray_icon instead. Also changed Context::set_tray_icon to accept Option<T>.
Context::default_window_icon_mut
Context::tray_icon_mut
Context::set_default_window_icon
Context::set_tray_icon
Option<T>