New Sylas W Bug

I was in a match with Sylas the other day and I noticed a bug on the 9.4 update with his W. I was able to consistently get that bug to reproduce every time I tried. I'll paste below the exact update that seems to have caused this.

W - Kingslayer ICON Icon border now glows when Sylas is within the max healing threshold

During my match I noticed that if Sylas was in a position which caused that icon to glow, he could cast W without mana. I would like to clarify exactly what I mean. If Sylas has enough mana to cast the ability, then it casts like normal. However if he did not have the needed mana amount, he could cast it without any mana. So simply put, any time I was low on HP and out of mana, I could still cast W without any mana for a good heal. This worked every time I tried it for that match.