PHP Laravel Error: Trying to access array offset on value of type null

Environment:
Laravel Version: 5.5
PHP Version: 7.4.0

Error stack trace:
Message: Trying to access array offset on value of type null

Sample code that gave me error:
$filterConfig = $request->get('filterConfig', null);
$showAll = $filterConfig['show']['all'] === 'true'? true: false;

The error was coming because $filterConfig was getting initialized by null in the first line and I was fetching $filterConfig[‘show’][‘all’] in the second line. Hence, it was throwing an error by saying Trying to access array offset on value of type null

NOTE: This error only comes if you have upgraded to PHP 7.4

Solution:

if (isset($filterConfig) && isset($filterConfig['show']['all'])) {
$showAll = true;
} else {
$showAll = false;
}

Chetan