Missing File Warning

Whenever I start Minecraft it says:

[08:53:53] [Client thread/WARN]: File minecraft:sounds/mob/ghast/fireball.ogg does not exist, cannot add it to event minecraft:item.fireCharge.use

I don't know what it means but i recently rebuilt my computer and it still did the same thing and I thought it would be important to tell Mojang because of its severity level in the logs of "WARN."