Sona and Kalista bug

Okay, simple and annoying bug. I flashed in to Crescendo and my ADC Kalista ulted me mid combo. Canceling my ult before it even went off while still going on cool down. You can hear the ult go threw but the projectile did not go or take the stunning effect. We were able to chase down one of the enemy but the Sivir escaped. This is kinda a big bug for something that stops a ult.