[MAYBE SOLVED] HTTPS site losing PHP connection overnight!

I think I have found the problem now that I have added declare(strict_types=1); to every system PHP file:

( ! ) Fatal error: Uncaught TypeError: filter_var(): Argument #3 ($options) must be of type array|int, null given in /var/www/ci4-strict.tk/system/HTTP/RequestTrait.php on line 341

The following KLUDGE fixes the problem:

File: /system/HTTP/RequestTrait.php on line 341

PHP Code:

# KLUDGE - 2021-03-05
   $flags = NULL ?: 0;

  return filter_var($value, $filter, $flags);
}// public function fetchGlobal($method, $index = null, $filter = null, $flags = null) 


Usually the site has previously gone down overnight and I will check again tomorrow to ensure the KLUDGE cures the problem... watch this space