New version migration does not work from asset bundles in build

[qlee01]

Hi,

tried to upgrade to new version 0.18; as title says, the included migration fails when loading a hair asset from an asset bundle, but only in builds, in editor it works fine. This is the error message:

NullReferenceException: Object reference not set to an instance of an object.
  at Unity.DemoTeam.Hair.HairAsset.PerformMigrationStep () [0x00000] in <00000000000000000000000000000000>:0 
  at Unity.DemoTeam.Hair.VersionedDataUtility.HandleVersionChange[T] (T ctx) [0x00000] in <00000000000000000000000000000000>:0 
  at UnityEngine.AssetBundle.LoadAsset_Internal (System.String name, System.Type type) [0x00000] in <00000000000000000000000000000000>:0 
  at UnityEngine.AssetBundle.LoadAsset[T] (System.String name) [0x00000] in <00000000000000000000000000000000>:0