The compositor crashes when a group node has an output that is connected
to the compositor output, but the group internally has no Group Output
node. That's because the derived node tree structure would return a null
origin socket for this case, but the null socket is not handled by the
code. To fix this, we assume the input socket in such cases.
Pull Request: https://projects.blender.org/blender/blender/pulls/142944
b73d085e88