Texture file has black background

When I exported this mesh 9 months ago, its texture file filled in all the spaces with blurred colors. Now, when I export the same model, the spaces are filled in with black. This is a problem because when I bring the mesh and UV into Unity, there are black seams all around the model. Is there a setting that will export a texture with blurred colors?

The model:


The old UV with blurred gaps:

The new UV with black gaps (bad!)


The mesh and UV in Unity, where seams are visible:

it is a bug!

link workaround: