From 9c80c453aa94eef3895bdfeb921dc5425351fab3 Mon Sep 17 00:00:00 2001
From: Dan Royer <dan@marginallyclever.com>
Date: Wed, 27 Sep 2023 13:54:24 -0700
Subject: [PATCH] more safety checks

---
 .../com/marginallyclever/nodegraphcore/Subgraph.java  | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/main/java/com/marginallyclever/nodegraphcore/Subgraph.java b/src/main/java/com/marginallyclever/nodegraphcore/Subgraph.java
index 2bc17ee..323c797 100644
--- a/src/main/java/com/marginallyclever/nodegraphcore/Subgraph.java
+++ b/src/main/java/com/marginallyclever/nodegraphcore/Subgraph.java
@@ -9,7 +9,7 @@
 public class Subgraph extends Node implements SupergraphInput, SupergraphOutput, PrintWithGraphics {
     private final Graph graph = new Graph();
 
-    private class VariablePair {
+    static class VariablePair {
         public Dock<?> superVariable;
         public Dock<?> subVariable;
 
@@ -43,11 +43,14 @@ public Subgraph(Graph graph) {
     /**
      * Stores a deep copy of the given graph and exposes the {@link SupergraphInput}s and {@link SupergraphOutput}s to
      * the supergraph.
-     * @param graph the {@link Graph} to store.
+     * @param graph the {@link Graph} to store.  A deep copy is made.
      */
     public void setGraph(Graph graph) {
         this.graph.clear();
-        this.graph.add(graph.deepCopy());
+
+        if(graph!=null) {
+            this.graph.add(graph.deepCopy());
+        }
 
         for(Node n : this.graph.getNodes()) {
             extractSupergraphInputs(n);
@@ -106,7 +109,7 @@ private void extractSupergraphInputs(Node n) {
     private int sortVariables(VariablePair a, VariablePair b) {
         // all input first
         int aIn = (a.subVariable  instanceof DockReceiving)?1:0;
-        int bIn = (a.subVariable  instanceof DockReceiving)?1:0;
+        int bIn = (b.subVariable  instanceof DockReceiving)?1:0;
         if(aIn != bIn) return aIn-bIn;
         // then sort by name alphabetically
         return a.subVariable.getName().compareTo(b.subVariable.getName());