Fix `Animation` not updating display on adding a single frame after clearing previous frames
Fix `Animation` not updating display on adding a single frame after clearing previous frames

ppy/osu-framework,peppy/osu-framework,ppy/osu-framework,peppy/osu-framework,peppy/osu-framework,smoogipooo/osu-framework,smoogipooo/osu-framework,ppy/osu-framework