kills my site if no longer can find an image size

I had the Mailpoet plugin active, told Image Sizes not to generate its image sizes, then disabled Mailpoet plugin, and Image Sizes brought down my site by infinitely generating these errors in debug.log:

PHP Notice: Undefined index: mailpoet_newsletter_max in /wp-content/plugins/image-sizes/views/settings/disable-sizes.php on line 87
PHP Notice: Trying to access array offset on value of type null in /wp-content/plugins/image-sizes/views/settings/disable-sizes.php on line 88
PHP Notice: Trying to access array offset on value of type null in /wp-content/plugins/image-sizes/views/settings/disable-sizes.php on line 92
PHP Notice: Trying to access array offset on value of type null in /wp-content/plugins/image-sizes/views/settings/disable-sizes.php on line 93

I finally solved it by going to Image Sizes settings’ page and moving this nulled size from Disabled to Enabled, then saved settings, then refreshed, then the image size was no longer displayed in either column.