problems with draw.php

Hello,

i love quiztool an i have some quizzes (in german) for my students,
but now i have found some problems. iI have not checked this quizzes for a long time.

the error is the follwing:
Fatal error: Uncaught Error: [] operator not supported for strings in /www/htdocs/w00a744a/wissen/wp-content/plugins/quiz-tool-lite/quizFrontEnd/draw.php:934 Stack trace: #0 /www/htdocs/w00a744a/wissen/wp-content/plugins/quiz-tool-lite/quizFrontEnd/draw.php(335): qtl_quiz_draw::generateQuizQuestions(Array, Array) #1 /www/htdocs/w00a744a/wissen/wp-content/plugins/quiz-tool-lite/quizFrontEnd/draw.php(42): qtl_quiz_draw::drawQuiz(‘2’) #2 /www/htdocs/w00a744a/wissen/wp-content/plugins/quiz-tool-lite/quizFrontEnd/draw.php(1619): qtl_quiz_draw::drawQuizPage(‘2’) #3 /www/htdocs/w00a744a/wissen/wp-includes/shortcodes.php(325): qtl_quiz_draw->startQuiz(Array, ”, ‘QTL-Quiz’) #4 [internal function]: do_shortcode_tag(Array) #5 /www/htdocs/w00a744a/wissen/wp-includes/shortcodes.php(199): preg_replace_callback(‘/\\[(\\[?)(QTL\\-Q…’, ‘do_shortcode_ta…’, ‘<p>Im folgenden…’) #6 /www/htdocs/w00a744a/wissen/wp-includes/class-wp-hook.php(286): do_shortcode(‘<p>Im folgenden…’) #7 /www/htdocs/w00a744a/wissen/wp-includes/plugin.php(208 in /www/htdocs/w00a744a/wissen/wp-content/plugins/quiz-tool-lite/quizFrontEnd/draw.php on line 934

i have php 7.2 and the latest wordpress version

can you help?
Thanks!

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