Bugfix #4770

When adding a new node in a group, the call to refresh input/output
sockets was called after a compositing update was executed.
Just moved this call 2 lines up.

This also uncommits the fix from Joilnen, the stack pointers in the node
system are *per definition* set. If NULL, it's an indication something
else is wrong.

source/blender/src/editnode.c

@@ -1338,8 +1338,8 @@ bNode *node_add_node(SpaceNode *snode, int type, float locx, float locy)
 			node->locy -= gnode->locy;
 		}
 
-		node_set_active(snode, node);
 		snode_verify_groups(snode);
+		node_set_active(snode, node);
 		
 		if(node->id)
 			id_us_plus(node->id);