Blender Git Loki

Bugfix #17929

Old bug (2.42): when using node material, transparent shadow did not work.
It was missing to set the proper 'pass flag'.

Do note an important difference with non-node materials for 'transparent shadow'.
If there are no nodes, it uses the color from the unshaded material. When it has
nodes, it uses the color output from the entire node tree, which is typically
from shaded materials. The latter is because node shaders have no support for
shade passes yet (it only outputs rgb + a).