Fix deadlock between sk component and sk build or import

Fix deadlock when skeletal mesh component is shown in the detail panel with physics body section category open and the skeletalmesh is re-importing or doing any other asyc task that need the game thread to not be stall.

import the attach fbx, you should get a skeletalmesh.

drop the skeletalmesh into the current level

select the skeletalmesh actor and open the component detail to the physic body category

when you see the category re-import the skeletal mesh

Result: deadlock