The issue was that `bNodeSocketValueVector` and `bNodeSocketValueRGBA` don't store the value at the same location in the struct. I kept the cases for `SOCK_VECTOR` and `SOCK_RGBA` completely separate for now, because they only share code by coincidence and not because they are actually the same. Eventually there could be a "Vector Input" node similar to the "RGB" node. Reviewers: fclem Differential Revision: https://developer.blender.org/D4472