[fire_charge] Fix critical attempt to index local 'ent'

mods/ITEMS/mcl_fire/fire_charge.lua

@@ -49,11 +49,13 @@ minetest.register_craftitem("mcl_fire:fire_charge", {
 		local shootpos = vector.add(pos, vector.multiply(dropdir, 0.51))
 		local fireball = add_entity(shootpos, "mobs_mc:blaze_fireball")
 		local ent = fireball:get_luaentity()
+		if ent then
 			ent._shot_from_dispenser = true
 			local v = ent.velocity or 1
 			fireball:set_velocity(vector.multiply(dropdir, v))
 			ent.switch = 1
 			stack:take_item()
+		end
 	end,
 })