Black artifacts appear near some seam edges in tile-based level when indirect lightmap filtering is set to gaussian with a value above 0

1. Open the attached project 'gaussian filtering artifacts at uv edges'
2. Open the scene 's5 - gaussian filter artifacts'
3. Let the scene bake with progressive lightmapper in automode (or manually bake)
4. Observe dark edges on the scene geometry in some places
5. In lightmap settings, Reduce indirect filtering to 0
6. Observe Black edges disappears

If inspected via Object Maps tab (Baked Intensity), it can be seen that turning on/off indirect filtering causes the dilated uv border to turn black in some places or generate black artifacts.