--- src/org/jgrapht/ext/DOTExporter.java	2010-11-27 23:36:27.000000000 -0600
+++ DOTExporter.java	2011-12-07 21:06:03.041369519 -0600
@@ -152,7 +152,7 @@
             if (vertexLabelProvider != null) {
                 labelName = vertexLabelProvider.getVertexName(v);
             }
-            Map<String, String> attributes = null;
+            Map<String, String> attributes = new HashMap<String, String>();;
             if (vertexAttributeProvider != null) {
                 attributes = vertexAttributeProvider.getComponentAttributes(v);
             }
@@ -200,14 +200,16 @@
         if (labelName != null) {
             out.print("label=\"" + labelName + "\" ");
         }
-        for (Map.Entry<String, String> entry : attributes.entrySet()) {
-            String name = entry.getKey();
-            if (name.equals("label")) {
-                // already handled by special case above
-                continue;
-            }
-            out.print(name + "=\"" + entry.getValue() + "\" ");
-        }
+	if (attributes != null) {
+	    for (Map.Entry<String, String> entry : attributes.entrySet()) {
+		String name = entry.getKey();
+		if (name.equals("label")) {
+		    // already handled by special case above
+		    continue;
+		}
+		out.print(name + "=\"" + entry.getValue() + "\" ");
+	    }
+	}
         out.print("]");
     }