Update Node.java

Author: i-make-robots

src/main/java/com/marginallyclever/nodegraphcore/Node.java

@@ -39,7 +39,7 @@ public abstract class Node {
     /**
      * The percentage of completion of this node.
      */
-    private AtomicInteger complete = new AtomicInteger(0);
+    private final AtomicInteger complete = new AtomicInteger(0);
 
     /**
      * Default constructor