Don't leave scores screen empty if no scores are present yet

[wooster0]

Addresses https://github.com/ppy/osu/discussions/23787

I originally wanted to set allowShowingResults to false (i.e. hide the "View results" button) if there are no results but because this involves an API request to fetch the scores that would mean all the scores would have to be fetched all at once so that it knows whether to hide or show the "View results" button on a beatmap. Because that would slow things down and be very inefficient, this still allows the user to view the scores screen but if there aren't any scores, it shows a text, which I think is at least for now better than nothing.

As for the testing of this, I wasn't sure how to not generate scores only for one specific test so I opted into not using SetUpSteps and doing it that way.

Before: (empty screen)

After:

It's not localizable yet but so are many other strings so I hope that's fine?