Plugin triigers PHP Warning

Hi, the plugin triggers following PHP Warning:

Warning: Undefined array key "wse_reviews_opt" in \wp-content\plugins\wc-ship-est\wse_functions.php on line 98

Stack Trace
1. {main}() \wp-admin\admin.php:0
2. do_action($hook_name = 'settings_page_wc-ship-est') \wp-admin\admin.php:259
3. WP_Hook->do_action($args = [0 => '']) \wp-includes\plugin.php:474
4. WP_Hook->apply_filters($value = '', $args = [0 => '']) \wp-includes\class-wp-hook.php:331
5. wse_admin('') \wp-includes\class-wp-hook.php:307

This happens unless something is selected in settings -> Google Reviews -> Prompt Location.