How to reproduce:
1. Download attached project file and open "Normal" Scene (you can see the Sphere in black color)
2. Open 'NewBakeShader' shader and turn on the last line in surf function

Actual result: WorldNormalVector using in surface shader can't get proper value in GI computing function, but if I return WorldNormalVector directly as final color I can get the right value

Reproduced with: 5.5.5f1, 5.6.4f1, 2017.1.2p2, 2017.2.0p1, 2017.3.0b7, 2018.1.0a2

With 2018.1.0a2 Sphere becomes white. On Shader inspector, error appears: Redefinition of "surfInputVertexNormal"
With 5.5.5f1 Sphere still appears black with the last line in surf function