Uncaught TypeError: Cannot read property 'length' of undefined

I constantly receive this error everytime i try to Save and Update records using the Editor plugin. I am using JQuery version 1.8.2 with DataTables 1.9.4 and Editor 1.2.3.

Here's my JS code so far

		<script>
			$(document).ready(function() {
				var editor;			
				editor = new $.fn.dataTable.Editor({
					"ajaxUrl": "'.SITE_AJAX.'ajax-custvpns.post.php",
					"domTable": "#custVPNList",
					"dbTable": "customer_vpns",
					"fields": [{
							"label": "VPN Friendly:",
							"name": "vpnFriendly",
							"type": "text"
						}, {
							"label": "Win Name:",
							"name": "vpnWinName",
							"type": "text"
						}, {
							"label": "Win Address:",
							"name": "vpnWinAddress",
							"type": "text"
						}, {
							"label": "Win User:",
							"name": "vpnWinUser",
							"type": "text"
						}, {
							"label": "Win Password:",
							"name": "vpnWinPass",
							"type": "password"
						}, {
							"label": "Win Domain:",
							"name": "vpnWinDomain",
							"type": "text"
						}
					]
				});
				
				// Create Record
				$("a.editor_create").on("click", function (e) {
					e.preventDefault();
					editor.create(
						"Create Customer VPN",
						{ "label": "Save", "fn": function () { editor.submit(); } }
					);
				});
				
				// Edit Record
				$("#custVPNList").on("click", "a.editor_edit", function (e) {
					e.preventDefault();
					editor.edit(
						$(this).parents("tr")[0],
						"Edit Customer VPN",
						{ "label": "Update", "fn": function () { editor.submit(); } }
					);
				});
			 
				// Delete Record
				$("#custVPNList").on("click", "a.editor_remove", function (e){
					e.preventDefault();
					editor.message("Are you sure you want to remove this VPN entry?");
					editor.remove(
						$(this).parents("tr")[0], 
						"Delete Customer VPN", 
						{ "label": "Confirm", "fn": function (){ editor.submit(); } }
					);
				});
				
				var custVPNTable;
				custVPNTable = $("#custVPNList").dataTable({
					"bJQueryUI": true,
					"sAjaxSource": "'.SITE_AJAX.'ajax-custvpns.src.php",
					"bDeferRender": true,
					"aoColumns": [
						{ "mData": "vpnFriendly" },
						{ "mData": "vpnWinName" },
						{ "mData": "vpnWinAddress" },
						{ "mData": "vpnWinUser" },
						{ "mData": "vpnWinPass" },
						{ "mData": "vpnWinDomain" },
						{
							"mData": null,
							"sClass": "right",
							"sDefaultContent": "<a href=\"\" class=\"editor_edit\">Edit</a> / <a href=\"\" class=\"editor_remove\">Delete</a>"
						}
					],
					"bProcessing": true,
					"sServerMethod": "POST",
					"sPaginationType": "full_numbers",
					"aLengthMenu": [[10, 25, 50, 100, -1], [10, 25, 50, 100, "All"]],
					"iDisplayLength": 25,
					"sDom": "<\"H\"<\"span6\"l><\"span6\"fr>>t<\"F\"<\"span6\"i><\"span6\"p>>",
				});			
			});
		</script>

Here's my Ajax code for the processing

	include_once('../../includes/config.php');

	$action = isset($_POST['action']) ? $_POST['action'] : NULL;
	$table = isset($_POST['table']) ? $_POST['table'] : NULL;
	$id = isset($_POST['id']) ? $_POST['id'] : NULL;
	$data = isset($_POST['data']) ? $_POST['data'] : NULL;
	
	$oCustomer = new \models\Customer();
	if($action == 'create')
	{
		$insFieldSQL = $insValueSQL = array();
		if($data)
		{
			foreach($data as $field => $value)
			{
				$insFieldSQL[] = $field;
				$insValueSQL[] = $value;
			}
		}
		
		$insCustSQL = "INSERT INTO ".$table." (".implode(', ',$insFieldSQL).")
					   VALUES ('".implode("', '",$insValueSQL)."')";
		
		$res = $oCustomer->insertCustDetails($insCustSQL);
		echo $res;
	}
	elseif($action == 'edit')
	{
		$updFieldSQL = $eFieldList = array();
		if($data)
		{
			foreach($data as $field => $value)
			{
				$updFieldSQL[] = $field." = '".$value."'";
				$eFieldList[] = $field."' => '".$value;
			}
		}
		
		$updateCustSQL = "UPDATE		".$table."
						  SET			".implode(', ',$updFieldSQL)."
						  WHERE 		vpnID = '".$id."'";
		
		$res = $oCustomer->updateCustDetails($updateCustSQL);
		//echo $res;
		
		$eResult = array('id' => $id, 'error' => '', 'fieldErrors' => array(), 'data' => array(), 'row' => array('DT_RowId' => $id,'vpnFriendly' => 'A1 Testing','vpnWinName' => 'A1_Testing_Auto','vpnWinAddress' => '192.168.105.21','vpnWinUser' => 'admin','vpnWinPass' => '','vpnWinDomain' => ''));
		echo json_encode($eResult);
	}
	elseif($action == 'remove')
	{
		$res = $oCustomer->deleteCustDetails($table,'vpnID',$data[0]);
		echo $res;
	}

When i create / update or delete a record my ajax script runs and updates via the Database but the editor popup stays open with the processing icon spinning. This is when i receive the Uncaught TypeError: Cannot read property 'length' of undefined error. I think this is to do with the ajax response as i don't really know what needs to be sent back once db update is successful.

Any help and advice would be greatly appreciated.