
Otherwise meta_calculate_drm_mode_refresh_rate returns 0.0, which results in non-sense refresh_interval_us. https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3982 fixed that happening before. This is intended to catch if it ever happens again. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3980>