Bug report: crash after click apply to asset in skeleton editor

ver 4.26.1
duplicate a skeleton (UE4_Mannequin_Skeleton in ‘project/Content/Mannequin/Character/Mesh/UE4_Mannequin_Skeleton.uasset’),
open it, the preview mesh is empty, don’t know why is empty, tried to copy the original skeleton’s skeletal mesh (SK_Mannequin) and paste to the duplicated skeleton, apply to asset, crash.
Always crash in this way!