[Polybrush] Overwritting an exported mesh asset makes the object in the scene invisible

To reproduce:
1. Create a cube in a scene
2. With any brush from Polybrush select the object, so that Polybrush Mesh script is added to it.
3. In the Polybrush Mesh Export Mesh Asset and save it into assets
4. In the Polybrush Mesh Export Mesh Asset and overwrite the previous one.
Expected result: The view in Scene view remains the same
Actual result: The cube in the scene becomes invisible

Reproduced on: 2019.3.0a10, Polybrush 1.0.0