Allowing the array of busses to be empty in each bus subset

This is kind of tricky.

At off hours, the busses arrays are empty, so we can't make sure they are not empty in the integration test.

Possibly there's a way to check what time it is, though for an integration test you usually want the results to be consistent, and I guess, in a way, they are this way.

Anyways, it's not clear to me what the solution is, but maybe it's a good idea to allow them to be empty now...