gutils: Add (nullable) annotation to g_get_prgname()
gutils: Add (nullable) annotation to g_get_prgname()

It can return NULL if no program name has been set yet (i.e.
g_set_prgname() has not been called from somewhere).

Signed-off-by: Philip Withnall <29c2a2ac2a854b9cf047275aa9de346d096be2e0@endlessm.com>

endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib