RANGER-1345: Added a null check in order to avoid possible Null pointer dereference errors

Signed-off-by: Velmurugan Periasamy <vel@apache.org>
diff --git a/ugsync/src/main/java/org/apache/ranger/ldapusersync/process/LdapPolicyMgrUserGroupBuilder.java b/ugsync/src/main/java/org/apache/ranger/ldapusersync/process/LdapPolicyMgrUserGroupBuilder.java
index 4c95907..f93083c 100644
--- a/ugsync/src/main/java/org/apache/ranger/ldapusersync/process/LdapPolicyMgrUserGroupBuilder.java
+++ b/ugsync/src/main/java/org/apache/ranger/ldapusersync/process/LdapPolicyMgrUserGroupBuilder.java
@@ -414,7 +414,7 @@
 		}	
 		
 		List<String> oldUsers = new ArrayList<String>();
-		if (groupUserInfo.getXuserInfo() != null) {
+		if (groupUserInfo != null && groupUserInfo.getXuserInfo() != null) {
 			for (XUserInfo xUserInfo : groupUserInfo.getXuserInfo()) {
 				oldUsers.add(xUserInfo.getName());
 			}