text can be null

Author: thurka

visualvm/heapviewer/src/com/sun/tools/visualvm/heapviewer/utils/HeapUtils.java

@@ -132,6 +132,7 @@ public static Instance instanceFromHtml(String html, Heap heap) {
 
 
     public static String htmlize(String text) {
+        if (text == null) return null;
         return text.replace(">", "&gt;").replace("<", "&lt;"); // NOI18N
     }