When a survey is called directly with move=movesubmit in the URL (without going through the normal survey start flow), the session is never fully initialized. As a result, $_SESSION[$this->LEMsessid]['insertarray'] is null when setArgs() is called during the submit process.
Under PHP 7.4, in_array() accepted null as the second argument silently. Under PHP 8.x, this throws a fatal TypeError, causing a 500 Internal Server Error.
This affects installations where surveys are triggered externally via direct submit URLs, for example:
/index.php/survey/index?move=movesubmit&thisstep=0&sid=999991&token={TOKEN}&lang=en

This is a common use case in panel research workflows where respondents are redirected directly to a completion/screenout/quota-full survey without going through the normal survey navigation.

Root Cause:
In application/helpers/SurveyRuntimeHelper.php, line 692, $_SESSION[$this->LEMsessid]['insertarray'] is accessed without checking whether it is set:
php// Current code (line 692):
if ($this->LEMsessid && !in_array("refurl", $_SESSION[$this->LEMsessid]['insertarray'])) {
When the session has not been initialized through the normal survey flow, insertarray is null, causing the fatal error under PHP 8.x.

Proposed Fix:
Add an isset check before the in_array call:
phpif ($this->LEMsessid
&& isset($_SESSION[$this->LEMsessid]['insertarray'])
&& !in_array("refurl", $_SESSION[$this->LEMsessid]['insertarray'])) {
This is a minimal, non-breaking fix that makes the behavior consistent with how PHP 7.4 handled the same situation silently.