[GAMEPLAY] Spell level-up button visual glitch

I experienced this bug while playing an intermediate bot match on Cho'Gath. I leveled up his 'E' skill first, and the notification that I could level up his 'W' skill remained on the screen for the remainder of the match. I believe I leveled up the skill while on the platform, on the shop screen, and then tabbed out to check a guide for Cho. I don't know how to reproduce this, as I have not yet been able to test it out any further. I have included a screenshot of the bug as a link.