Also makes `CreatePlayerRuleset()` and `CreateRulesetForSkinProvider()` not-null to avoid unwanted behaviour with their derivers
Happens on cases like restarting the test scene by clicking directly on it on the browser (*where it for some reason reloads the entire test scene*)
ModTestScene
CreateRuleset
PlayerTestScene
SkinnableTestScene
Disable undo/redo menu items when they can't be performed
Hide edit context menu item in multiplayer song select
Fix 0 custom sample bank not falling back to user skin
Fix osu!mania replays actuating incorrect keys when multiple stages are involved
Fix typo in DrawableTaikoHitObject
Fade playfield to red when player health is low
Mark dummy api test scene as headless
Make beatmap carousel select recommended difficulties
Add support for testing arbitrary API requests/responses via Dummy API
Fix beatmap background not displaying when video is present