The test was checking the test scene's own `SelectedMods` bindable
rather than the multiplayer screen's, and the former was never actually
being mutated by anything. Therefore the case would pass even on
`master` with the fix reverted.
All other similar UI components have required dependencies, so this is
mainly to bring things in line with expectations. I am using this fact
in the skin editor to only show components which can be used in the
current editor context (by `try-catch`ing their
`Activator.CreateInstance`).