WitherSkulls flash for a brief moment when being summoned

Since minecraft updated to 1.7, there was the /summon command. This allowed you to summon projectiles with NBT tags to determine direction and other traits. The wither skull and small fireball projectile are some of these. However, when the command is put in and entered, the wither skull or small fireball will appear for a brief moment, then cease to exist. This does not happen with the arrow or normal fireball.

Steps to reproduce:
1. enter this command: "/summon WitherSkull ~ ~ ~

{ExplosionPower:1,direction:[0.0,0.0,0.0]}

or
/summon SmallFireball ~ ~ ~

{ExplosionPower:1,direction:[0.0,0.0,0.0]}

2.Watch as it disappears.