Fix cross-thread list manipulation in `SkinProvidingContainer`
Fix cross-thread list manipulation in `SkinProvidingContainer`

smoogipoo/osu,ppy/osu,peppy/osu,NeoAdonis/osu,smoogipooo/osu,ppy/osu,ppy/osu,smoogipoo/osu,NeoAdonis/osu,smoogipoo/osu,NeoAdonis/osu,peppy/osu-new,peppy/osu,peppy/osu