Actually search the part's nodes for non-top/bottom

It does help if one fetches the node before testing it.

Source/DisposablePad/DisposablePad.cs

@@ -226,6 +226,7 @@ AttachNode FindNode (Part p)
 				}
 			}
 			for (int i = 0; i < p.attachNodes.Count; i++) {
+				node = p.attachNodes[i];
 				if (node.attachedPart == null) {
 					return node;
 				}