When making a node group always add one input and one output node, regardless of whether there are any exposed sockets. The standard common case is that some sockets will eventually have to be exposed anyway, and it's easier to just delete the unused node instead of having to look it up in the menu.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55442 954f8c5b-7b00-dc11-b283-0030488c597c