retrieving multiple related data using oData_EndPoint

 Hi,
 I am trying retrieve multiple lookup fields of an entity into another entity(Main form). So I used oData query to retrieve them.
 I was able to pull the data but stuck at avoiding null values. I am receiving 'Unable to get property of undefined or null reference' error.

 How can I pull data without null values? Here is my code..

function HideTabOnLoad()
 {
   var userName=Xrm.Page.context.getUserName();
   var entitiesLookup= RetrieveEntities();
 }

function RetrieveEntities()
{
debugger;
var ClientUrl=Xrm.Page.context.getClientUrl();
var oData_EndPoint="/XRMServices/2011/OrganizationData.svc";
var oData_EntityCollection="/new_securitySet";
var Query="?$select=new_new_entities_new_security_Entity/new_entities,new_new_entities_new_security_Entity1/new_entities,new_new_entities_new_security_Entity2/new_entities,new_new_entities_new_security_Entity3/new_entities,new_new_entities_new_security_Entity4/new_entities&$expand=new_new_entities_new_security_Entity,new_new_entities_new_security_Entity1,new_new_entities_new_security_Entity2,new_new_entities_new_security_Entity3,new_new_entities_new_security_Entity4";
var URL=ClientUrl+oData_EndPoint+oData_EntityCollection+Query;

//synchronous XMLHttpRequest to retrieve account record
   var req=new XMLHttpRequest();
   req.open("GET",encodeURI(URL),false);
   req.setRequestHeader("Accept","application/json");
   req.setRequestHeader("Content-Type","application/json;charset=utf-8");
   req.send(null);
   var records = JSON.parse(req.responseText).d;
  for(var i=0;i<records.results.length;i++)
  {
  if(records.results[i]!=null)
  {
  var securityEntity=records.results[i];
  var entity=securityEntity.new_new_entities_new_security_Entity.new_entities;
  alert(entity);
  var entity1=securityEntity.new_new_entities_new_security_Entity1.new_entities;
  alert(entity1);
  var entity2=securityEntity.new_new_entities_new_security_Entity2.new_entities;
  alert(entity2);
  var entity3=securityEntity.new_new_entities_new_security_Entity3.new_entities;
  alert(entity3);
  var entity4=securityEntity.new_new_entities_new_security_Entity4.new_entities;
  alert(entity4);
  }
  }
}