
This fixes an issue where xrandr reports the preferred mode of an internal laptop display twice. This triggered an assertion that crashed GDM, because meta_monitor_normal_generate_modes assumes that the list of display nodes doesn't contain duplicate pointers to the preferred one. Closes: <https://gitlab.gnome.org/GNOME/mutter/-/issues/2945> Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3176>