ErrorException: Deprecated: rtrim(): Passing null to parameter #1 ($string) of type string is deprecated

[archon810]

PHP 8.1 throws this:

ErrorException: Deprecated: rtrim(): Passing null to parameter #1 ($string) of type string is deprecated
#8 /wp-content/plugins/wp-api-swaggerui/wp-api-swaggerui.php(120): WP_API_SwaggerUI::getBasePath
#7 /wp-content/plugins/wp-api-swaggerui/wp-api-swaggerui.php(92): WP_API_SwaggerUI::swagger
#6 /wordpress/wp-includes/class-wp-hook.php(324): WP_Hook::apply_filters
#5 /wordpress/wp-includes/class-wp-hook.php(348): WP_Hook::do_action
#4 /wordpress/wp-includes/plugin.php(565): do_action_ref_array
#3 /wordpress/wp-includes/class-wp.php(835): WP::main
#2 /wordpress/wp-includes/functions.php(1342): wp
#1 /wordpress/wp-blog-header.php(16): require
#0 /index.php(23): null