PHP 8 Deprecated function: class_exists(): Passing null to parameter #1

https://www.drupal.org/project/entityreference/releases/7.x-1.6-rc2

PHP used 8.1.8
Need help and update/solution/patch:

Deprecated function: class_exists(): Passing null to parameter #1 ($class) of type string is deprecated in _entityreference_get_behavior_handler() (line 197 from /modules/entityreference/entityreference.module).

Code of file in that place:
190 function _entityreference_get_behavior_handler($behavior) {
191 $object_cache = drupal_static(__FUNCTION__);
192
193 if (!isset($object_cache[$behavior])) {
194 ctools_include('plugins');
195 $class = ctools_plugin_load_class('entityreference', 'behavior', $behavior, 'class');
196
197 $class = class_exists($class) ? $class : 'EntityReference_BehaviorHandler_Broken';
198 $object_cache[$behavior] = new $class($behavior);
199 }
200
201 return $object_cache[$behavior];
202 }

@Tesam, you need to upgrade to

1.6.1-rc3

https://www.drupal.org/project/entityreference/releases/7.x-1.6-rc3

https://www.drupal.org/project/entityreference/releases/7.x-1.7

please try the latest release

https://www.drupal.org/project/entityreference/releases/7.x-1.9