https://github.com/enemeez/simplefarming/blob/8f24a4d136ccb5a7c356fff84462e4fff24a2867/src/main/java/enemeez/simplefarming/items/GrainItem.java#L21

Right-clicking with corn in your hand while trying to mount an entity that does not extend AgeableEntity causes a server crash, for example the Beetle from Druidcraft.