Your Site is Experiencing a Technical Issue

Every time I deactivate and reactivate a plugin I get the following message: “There has been a critical error on this website. Please check your site admin email inbox for instructions.” In the email, it says there is an error in admin-ajax.php and it gives me the trace:

An error of type E_ERROR was caused in line 1126 of the file /home/gdynia06/zip-pilates-studio.com/www/wp-content/plugins/getwid/includes/.includes.php. Error message: Uncaught Error: Attempt to modify property "files" on null in /home/gdynia06/zip-pilates-studio.com/www/wp-content/plugins/getwid/includes/.includes.php:1126
Stack trace:
#0 /home/gdynia06/zip-pilates-studio.com/www/wp-content/plugins/getwid/includes/.includes.php(1144): ae7492186dddc84093b7cbb63c9381f7f->a0026a96024fbf3c1bbe6bd6e61c452f2()
#1 /home/gdynia06/zip-pilates-studio.com/www/wp-content/plugins/getwid/includes/.includes.php(1907): ae7492186dddc84093b7cbb63c9381f7f->install()
#2 /home/gdynia06/zip-pilates-studio.com/www/wp-content/plugins/getwid/includes/.includes.php(2015): ae7492186dddc84093b7cbb63c9381f7f->aa34bdabad6544f7298e6015b877a3026()

#3 /home/gdynia06/zip-pilates-studio.com/www/wp-includes/class-wp-hook.php(303): ae7492186dddc84093b7cbb63c9381f7f::a70483a27a4211ba1ff781636317ff87d('')
#4 /home/gdynia06/zip-pilates-studio.com/www/wp-includes/class-wp-hook.php(327): WP_Hook->apply_filters(NULL, Array)
#5 /home/gdynia06/zip-pilates-studio.com/www/wp-includes/plugin.php(470): WP_Hook->do_action(Array)
#6 /home/gdynia06/zip-pilates-studio.com/www/wp-settings.php(578): do_action('init')
#7 /home/gdynia06/zip-pilates-studio.com/www/wp-config.php(96): require_once('/home/gdynia06/...')
#8 /home/gdynia06/zip-pilates-studio.com/www/wp-load.php(37): require_once('/home/gdynia06/...')
#9 /home/gdynia06/zip-pilates-studio.com/www/wp-admin/admin-ajax.php(22): require_once('/home/gdynia06/...')
#10 {main}
  thrown

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