LIVE: ProjectileMovement component does not function when a PrimitiveComponent is missing or removed from the Components

A projectile brought over from 4.5.1 or earlier that does not have a Primitive Component as the Root, or removing the root from the projectile in 4.6, returns an error: "Movement component [ProjectileMovement Name] must update a PrimitiveComponent, but owning actor [ProjectileBP Name] does not have a root PrimitiveComponent. Auto registration failed."

This affects projectile blueprints brought over from 4.5 or earlier (in which it does cause a problem) that do not have a primitive component as the root. This also affects any projectiles in 4.6 that have the root component deleted and replaced, including those replaced with primitive components.

Duplicating the ProjectileMovement component and deleting the original returns the projectile movement to normal, whether there is a primitive component as the root or not.

First noted in a Paper2d project, but reproduced in a First Person Blueprint template project as well.

1. Launch: UE4Editor.exe
2. Create a new First Person Blueprint template project
3. Open the MyProjectile blueprint
4. Delete the [ROOT] CollisionComponent
5. PIE
6. Fire your weapon

Results:
The projectile is spawned but does not use any of the values in the ProjectileMovement component (Projectile). After PIE ends, there are Play In Editor errors: "Movement component Projectile must update a PrimitiveComponent, but owning actor 'MyProjectile_C_x' does not have a root PrimitiveComponent. Auto registration failed."