Gameplay Visual bug on leveling-up spell's visual

Yersteday (saturday 30/04/16) I launched a game with Sandra and after taking 1 point in my Q spell, the icon for leveling up spell was still visible on my W, and it stayed here until the end! it was just a visual bug cause I couldn't get any point in the spell as long as I had no point to spend.

I don't know what I did to get this bug, and here are 3 screenshots from different moments of the game: http://zupimages.net/up/16/17/6d3h.tiff http://zupimages.net/up/16/17/pgg2.tiff http://zupimages.net/up/16/17/mkpr.tiff