Warning: mysqli_fetch_assoc() expects parameter 1 to be mysqli_result

Bij het omzetten van MySQL naar mysqli krijg ik deze foutmelding: Warning: mysqli_fetch_assoc() expects parameter 1 to be mysqli_result, object given in C:\domains\hermans-motorhomes.be\wwwroot\gastenboekb_ingeven.php on line 56

<?php require_once('Connections/con_gastenboek.php'); ?>
<?php
// Load the common classes
require_once('includes/common/KT_common.php');

// Load the tNG classes
require_once('includes/tng/tNG.inc.php');

// Make a transaction dispatcher instance
$tNGs = new tNG_dispatcher("");

// Make unified connection variable
$conn_con_gastenboek = new KT_connection($con_gastenboek, $database_con_gastenboek);

// Start trigger
$formValidation = new tNG_FormValidation();
$formValidation->addField("emailaddress", true, "text", "email", "", "", "");
$formValidation->addField("website", false, "text", "url", "", "", "");
$formValidation->addField("onderwerp", true, "text", "", "", "", "");
$formValidation->addField("message", true, "text", "", "", "", "");
$tNGs->prepareValidation($formValidation);
// End trigger

//start CheckCaptcha trigger
//remove this line if you want to edit the code by hand
function CheckCaptcha(&$tNG) {
$captcha = new tNG_Captcha("captcha_id_id", $tNG);
$captcha->setFormField("POST", "captcha_id");
$captcha->setErrorMsg("Code komt niet overeen met de afbeelding");
return $captcha->Execute();
}
//end CheckCaptcha trigger

// Make an insert transaction instance
$ins_users = new tNG_insert($con_gastenboek, $conn_con_gastenboek);
$tNGs->addTransaction($ins_users);
// Register triggers
$ins_users->registerTrigger("STARTER", "Trigger_Default_Starter", 1, "POST", "KT_Insert1");
$ins_users->registerTrigger("BEFORE", "Trigger_Default_FormValidation", 10, $formValidation);
$ins_users->registerTrigger("END", "Trigger_Default_Redirect", 99, "gastenboekb.php");
$ins_users->registerTrigger("BEFORE", "CheckCaptcha", 10);
// Add columns
$ins_users->setTable("users");
$ins_users->addColumn("username", "STRING_TYPE", "POST", "username");
$ins_users->addColumn("emailaddress", "STRING_TYPE", "POST", "emailaddress");
$ins_users->addColumn("onderwerp", "STRING_TYPE", "POST", "onderwerp");
$ins_users->addColumn("message", "STRING_TYPE", "POST", "message");
$ins_users->addColumn("datum_van", "STRING_TYPE", "POST", "datumveld");
$ins_users->setPrimaryKey("userid", "NUMERIC_TYPE");

// Execute all the registered transactions
$tNGs->executeTransactions();

// Get the transaction recordset ************ hieronder staan de twee en derde regel die de fout geven****
$rsusers = $tNGs->getRecordset("users");
$row_rsusers = mysqli_fetch_assoc($rsusers);
$totalRows_rsusers = mysqli_num_rows($rsusers);

// Captcha Image
$captcha_id_obj = new KT_CaptchaImage("captcha_id_id");
// datum bepalen //
$vandaag = date("Y-m-d");
// einde datum //
?>