Return an empty string if email is null. JM-778

git-svn-id: http://svn.igniterealtime.org/svn/repos/wildfire/branches@4443 b35dd754-fafc-0310-a699-88a17e54d16e

3_0_branch/src/java/org/jivesoftware/wildfire/user/User.java

@@ -180,7 +180,7 @@ public class User implements Cacheable {
     }
 
     public String getEmail() {
-        return email;
+        return email == null ? "" : email;
     }
 
     public void setEmail(String email) {