Since the fireball is source of light it is logical that there should be no shadow from it.

But if we take a look from scientific point of wiew the fireball can actually create the shadow. How? To create a fireball you actually need some flamable material which you can tos. And it is likely that this material isn't compleetly transparent so it blocks the light coming through.
But wait just before I sad that firebal is actually a light source. So how could it posibly create the shadow? Well the fire itself does emits the light but the amount of light is limited. So if you would tos a firebal during the day in high sunlight you would actualy see vague shadow beneath the firebal since the amount of light that fire emits is much lower than the amount of light that it comes from the sun.

Anywhay generally there should be no shadow beneath the fireball.
I don't think I can remember any game with shadow benath the firebals.