Problem with QSM plugin

I use QSM plugin (Quiz And Survey Master). During the scaning process, I saw http 500 error in debug console. In error.log on the server, I see:

PHP Fatal error:  Uncaught TypeError: count(): Argument #1 ($var) must be of type Countable|array, string given in plugins/quiz-master-next/php/classes/class-qmn-quiz-manager.php:603
Stack trace:
#0 plugins/quiz-master-next/php/classes/class-qmn-quiz-manager.php(870): QMNQuizManager->load_questions('8', Object(stdClass), true, 0)
#1 plugins/quiz-master-next/php/classes/class-qmn-quiz-manager.php(467): QMNQuizManager->display_quiz(Object(stdClass), Array, 0, Array)
#2 public_html/wp-includes/shortcodes.php(356): QMNQuizManager->display_shortcode(Array, '', 'mlw_quizmaster')
#3 [internal function]: do_shortcode_tag(Array)
#4 public_html/wp-includes/shortcodes.php(228): preg_replace_callback('/\\[(\\[?)(mlw_qu...', 'do_shortcode_ta...', '[mlw_quizmaster...')
#5 plugins/media-cleaner/classes/core.php(264): do_shortcode('[mlw_quizmaster...')
#6 plugins/media-cleaner/classes/parsers/common.php(105): Meow_WPMC_Core->get_urls_from_html('[mlw_quizmaster...')
#7 public_html/wp-includes/class-wp-hook.php(307): MeowApps_WPMC_Parser_Common->scan_post('[mlw_quizmaster...', '81186')
...