Fatal error when changing setting

Hello,

I was adjusting the content of the e-mail sent when a product is back in stock resulting in the following fatal error:

Fatal error: Uncaught TypeError: Cannot access offset of type string on string in /var/www/virtual/myrkstore.is/htdocs/wp-content/plugins/back-in-stock-notifier-for-woocommerce/includes/class-copy-mailer.php:42 Stack trace: #0 /var/www/virtual/myrkstore.is/htdocs/wp-includes/class-wp-hook.php(324): CWG_Copy_Mailer->default_values() #1 /var/www/virtual/myrkstore.is/htdocs/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters() #2 /var/www/virtual/myrkstore.is/htdocs/wp-includes/plugin.php(517): WP_Hook->do_action() #3 /var/www/virtual/myrkstore.is/htdocs/wp-content/plugins/back-in-stock-notifier-for-woocommerce/includes/admin/class-settings.php(752): do_action() #4 /var/www/virtual/myrkstore.is/htdocs/wp-includes/class-wp-hook.php(324): CWG_Instock_Settings->default_value() #5 /var/www/virtual/myrkstore.is/htdocs/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters() #6 /var/www/virtual/myrkstore.is/htdocs/wp-includes/plugin.php(517): WP_Hook->do_action() #7 /var/www/virtual/myrkstore.is/htdocs/wp-admin/admin.php(175): do_action() #8 /var/www/virtual/myrkstore.is/htdocs/wp-admin/edit.php(10): require_once(‘…’) #9 {main} thrown in?/var/www/virtual/myrkstore.is/htdocs/wp-content/plugins/back-in-stock-notifier-for-woocommerce/includes/class-copy-mailer.php?on line?42

Now I am unable to use the plugin.

There is probably an easy fix to this I haven’t figured out yet.
Any ideas please?

Thanks in advance.