Additives using Frame From This Animation as the Base Pose Type fail to retarget correctly

Additive animations that use a frame from their own sequence as a base pose are initially broken when retargeted.  Users have to refresh the properties that select the base pose in order to fix the issue after the new sequence has been generated.  This may be related to [Link Removed] as that also affects additives. 

1. Open whatever animation is going to be your source
2. Change Additive Anim Type to Local Space or Mesh Space
3. Change the Base Pose Type to Frame From This Animation
4. Set the Ref Frame Index to some value
5. Now retarget the animation using the offline retarget workflow in the editor
   1. Make sure the Retain Additive Flags value is set during the retarget workflow
6. Open the generated animation
   1. Expected behaviour: the pose is correct
   2. Actual behaviour: the pose is broken until you change the Base Pose Type or Ref Frame Index