Column 'RefQid' cannot be null หมายความว่ายังไงครับ code ด้านใน

<?php require_once('Connections/apartment.php'); ?>
<?php
if (!function_exists("GetSQLValueString")) {
function GetSQLValueString($theValue, $theType, $theDefinedValue = "", $theNotDefinedValue = "") 
{
  if (PHP_VERSION < 6) {
    $theValue = get_magic_quotes_gpc() ? stripslashes($theValue) : $theValue;
  }

  $theValue = function_exists("mysql_real_escape_string") ? mysql_real_escape_string($theValue) : mysql_escape_string($theValue);

  switch ($theType) {
    case "text":
      $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL";
      break;    
    case "long":
    case "int":
      $theValue = ($theValue != "") ? intval($theValue) : "NULL";
      break;
    case "double":
      $theValue = ($theValue != "") ? doubleval($theValue) : "NULL";
      break;
    case "date":
      $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL";
      break;
    case "defined":
      $theValue = ($theValue != "") ? $theDefinedValue : $theNotDefinedValue;
      break;
  }
  return $theValue;
}
}

$editFormAction = $_SERVER['PHP_SELF'];
if (isset($_SERVER['QUERY_STRING'])) {
  $editFormAction .= "?" . htmlentities($_SERVER['QUERY_STRING']);
}

if ((isset($_POST["MM_insert"])) && ($_POST["MM_insert"] == "form1")) {
  $insertSQL = sprintf("INSERT INTO tbanswer (ADetail, AName, AEmail, ADate, RefQid) VALUES (%s, %s, %s, %s, %s)",
                       GetSQLValueString($_POST['ADetail'], "text"),
                       GetSQLValueString($_POST['AName'], "text"),
                       GetSQLValueString($_POST['AEmail'], "text"),
                       GetSQLValueString($_POST['ADate'], "date"),
                       GetSQLValueString($_POST['RefQid'], "int"));

  mysql_select_db($database_apartment, $apartment);
  $Result1 = mysql_query($insertSQL, $apartment) or die(mysql_error());

  $insertGoTo = "answer_save.php";
  if (isset($_SERVER['QUERY_STRING'])) {
    $insertGoTo .= (strpos($insertGoTo, '?')) ? "&" : "?";
    $insertGoTo .= $_SERVER['QUERY_STRING'];
  }
  header(sprintf("Location: %s", $insertGoTo));
}

$colname_DetailRS1 = "-1";
if (isset($_GET['recordID'])) {
  $colname_DetailRS1 = $_GET['recordID'];
}
mysql_select_db($database_apartment, $apartment);
$query_DetailRS1 = sprintf("SELECT * FROM tbquestion WHERE Qid = %s", GetSQLValueString($colname_DetailRS1, "int"));
$DetailRS1 = mysql_query($query_DetailRS1, $apartment) or die(mysql_error());
$row_DetailRS1 = mysql_fetch_assoc($DetailRS1);
$totalRows_DetailRS1 = mysql_num_rows($DetailRS1);

$colname_Recordset2 = "-1";
if (isset($_GET['RefQid'])) {
  $colname_Recordset2 = $_GET['RefQid'];
}
mysql_select_db($database_apartment, $apartment);
$query_Recordset2 = sprintf("SELECT * FROM tbanswer WHERE RefQid = %s", GetSQLValueString($colname_Recordset2, "int"));
$Recordset2 = mysql_query($query_Recordset2, $apartment) or die(mysql_error());
$row_Recordset2 = mysql_fetch_assoc($Recordset2);
$totalRows_Recordset2 = mysql_num_rows($Recordset2);
?>

<?php
mysql_free_result($DetailRS1);

mysql_free_result($Recordset2);
?>