[GAMEPLAY] Assists on Dragon don't give 5 Devourer stacks

Assists on Dragon as with the Devourer item only give 1 stack instead of the 5 stated in the tooltip. This can happen with any champion at any point in the game. It can be worked around if you know it, but it is very inconvenient and can result in blue/red smite being down for critical fights when it otherwise wouldn't be. Steps to reproduce:

1. Enter custom game with another player, take smite but play any champion.
2. Buy devourer.
3. Kill the dragon, but let your ally get the last hit.
4. You should get 1 devourer stack, instead of the intended 5.