PHP errors

Hi,

There are a lot of errors in the error log relating to WP Google Analytics Events. How can I fix these please? The errors are as follows:

PHP message: PHP Notice: Undefined offset: 6 in /www/happy_114/public/wp-content/plugins/wp-google-analytics-events/ga-scroll-event.php on line 236" while reading response header from upstream, client: 185.110.36.159, server: www.happy.co.uk, request: "GET /course/intensives/introduction-to-power-bi-desktop/ HTTP/1.0", upstream: "fastcgi://unix:/var/run/php7.2-fpm-happy.sock:", host: "www.happy.co.uk"

PHP message: PHP Notice: Undefined offset: 0 in /www/happy_114/public/wp-content/plugins/wp-google-analytics-events/ga-scroll-event.php on line 223

PHP message: PHP Notice: Undefined index: gst in /www/happy_114/public/wp-content/plugins/wp-google-analytics-events/ga-scroll-event.php on line 143

PHP message: PHP Notice: Undefined index: gtm in /www/happy_114/public/wp-content/plugins/wp-google-analytics-events/ga-scroll-event.php on line 142

Many thanks