REPO-2516 - MNT-17845: Added a null check on the noderef

git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/BRANCHES/DEV/5.2.N/root@137796 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/repo/virtual/ref/Reference.java

@@ -115,6 +115,8 @@ public class Reference
      *
      */
     public static final Reference fromNodeRef(NodeRef nodeRef)
+    {
+        if (nodeRef != null)
         {
             String id = nodeRef.getId();
             if (id.startsWith("" + VIRTUAL_TOKEN) && (id.length() > 1)) // belts-and-braces
@@ -143,7 +145,7 @@ public class Reference
                         logger.debug("Encoding exception:", ree);
                         return null;
                     }
-
+                }
             }
         }
         return null;