PHP Compatability Issue ?

Problem/Motivation

Following Warning / Notice Occurs in PHP 7.3+
Notice: Array to string conversion in Drupal\Core\Routing\RouteProvider->preLoadRoutes() (line 222 of core/lib/Drupal/Core/Routing/RouteProvider.php).
• Notice: Array to string conversion in Drupal\Core\Database\Statement->execute() (line 59 of core/lib/Drupal/Core/Database/Statement.php).
• Warning: Illegal offset type in isset or empty in Drupal\Core\Routing\RouteProvider->getRoutesByNames() (line 253 of core/lib/Drupal/Core/Routing/RouteProvider.php).
• Warning: Illegal offset type in isset or empty in Drupal\Core\Routing\RouteProvider->getRoutesByNames() (line 253 of core/lib/Drupal/Core/Routing/RouteProvider.php).
• Warning: array_flip(): Can only flip STRING and INTEGER values! in Drupal\Core\Routing\RouteProvider->getRoutesByNames() (line 259 of core/lib/Drupal/Core/Routing/RouteProvider.php).
• Notice: Array to string conversion in Drupal\Core\Routing\RouteProvider->getRouteByName() (line 208 of core/lib/Drupal/Core/Routing/RouteProvider.php).

Steps to reproduce

Enable & configure latest version of the restrict_ip module in Drupal Core 8.8.x (or) 8.9.x. On every admin page visit the error would occur

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet