If the null-checks were tripped, the test would crash anyway. It is not
possible to call `.Any()` and get a valid result instead of an exception
on a null reference.
The slight hack which was used in the test to ensure that the mod
settings overlay covered the entire width of the mod overlay broke after
adjustments to the layout in the previous commit.
Locally adjust the hack to use the parent of the `ModSettingsContainer`
rather than the container itself.