This was causing any `ValueChanged` event bind (such as the one in
`SettingsItem` to invoke `SettingsChanged`) to be overwritten when
`Current` is set afterwards.
I guess the changes that involved `MultiplayerTestScene` having a test
user lookup cache caused this test case to false-pass silently.
Added an explicit assert which ensures the added user indeed has a null
`User` value.
Consider this a request for comment. It's the cleanest solution I can
come up with without dropping either the blur, or use of
`ModelBackedDrawable`.
Intended to resolve https://github.com/ppy/osu/issues/14276.
- make `UserActivity.InGame` and derive that to `InSoloGame` and `InMultiplayerGame`
- rename `SoloGame` to `InSoloGame`
- rename `MultiplayerGame` to `InMultiplayerGame`