[GAMEPLAY] Spells not damaging targets when leaving vision(Only seen on new SR for me at this point)

I was playing Veigar against a Katarina, in a follow to the bottom lane the kat was below 200 health, and which point I fired my ult at her, my ultimate animation was traveling towards her but as soon as she entered the brush my ultimate did not hit her as she left the brush unscathed and my ult cooldown refreshed, however she was able to get away as i did not pursue further with certainty that she would be slain by it.