LI Property Override: LI internal references are broken when saving the overrides.

When Saving the level, ULevelInstancePropertyOverrideAsset::SerializeActorPropertyOverrides will run UStruct::SerializeTaggedProperties to "diff-serialize" each object against its archetype (the LI default values). The references (direct, soft, weak...) are pointing at the temporary assets when the archetypes are pointing at the LI level's assets.  This results in generating an override on the temp assets which cannot be resolved at PIE or cook time. 

• Unzip the attached project
• Launch the editor
• Override LI_Showcase 
  • Right-click Level\Override
  • Select Pointlight and change the color (or any other property)
  • Save
• Enter Pie. 
• Inspect InternalReferencer
  • its Light and 'New Var" members (soft refs) are pointing a /Temp... actors that don't exists