This used to already be the case prior to b419ea7, but in a very
roundabout way. Changes to the value of the star difficulty bindable -
including indirect changes via the set of active mods changing - would
trigger the wedge display to regenerate and load asynchronously.
b419ea7 accidentally broke this by moving down the bindable retrieval to
a lower level, at which point `WedgeInfoText` would only receive the set
of mods selected at the time at which a given beatmap was selected, and
not receive any further updates, breaking the BPM display updating in
real time (as `WedgeInfoText` could not be aware that rate-changing mods
were even in effect).
To resolve, explicitly reload the wedge's contents on mod changes.
This fixes the whole issue behind `Ruleset.Value` being null, by
updating `Current` on BDL rather than waiting for the base logic which
executes at `LoadComplete`.
This seems like something that should happen at the base `TabControl` class itself, by switching `Current` right after the first added tab item, rather than doing it on `LoadComplete`, but I'm not sure about changing framework logic outright, so fixing this locally until it occurs on other places.