It's not valid in the base `HitErrorMeter`, as the colour meter only
displays colour for a given judgement, so it is still valid to add new
items to it even if the hit window is 0, as misses are still possible.
`CatchHitWindows` were a vestige from the past, and were not actually
used anywhere except for the hit error meter test, giving off an
appearance that the hit error meter was working properly.
`CatchHitObject` actually specifies empty hit windows.