ThemedIcon.useDefaultFallbacks

Whether to use the default fallbacks found by shortening the icon name at '-' characters. If the "names" array has more than one element, ignores any past the first.

For example, if the icon name was "gnome-dev-cdrom-audio", the array would become

{
  "gnome-dev-cdrom-audio",
  "gnome-dev-cdrom",
  "gnome-dev",
  "gnome",
  NULL
};