Steps to reproduce:

1) Download attached project " ImportAssetTest.zip" and open in Unity.
2) In Project tab, go to Assets >> Art >> Buildings >> Commercial >> Generated, click on "Shop_hiden_hitech01_1x1" asset and check the values in
Inspector tab (see attached image "Values.png").
3) Close Unity, delete Library folder from the Project path.
4) Open Unity again, In Project tab, go to Assets >> Art >> Buildings >> Commercial >> Generated, click on "Shop_hiden_hitech01_1x1" asset and check the values in Inspector tab (see attached image "ValuesNULL.png").

Reproduced with: 5.3.0f4, 5.3.5p2, 5.4.0b21.

Not reproduced with : 5.2.4f1