PHP 8.1 deprecated warning

[Sweetchuck]

To Reproduce
PHP 8.1
drush/drush 11.0.5
Custom test which uses the \Drush\TestTraits\DrushTestTrait::drush()
The optional $suffix = null argument causes the problem.
$cmd[] = $suffix;
$exec = array_filter($cmd, 'strlen');

Expected behavior
No warnings and errors.

Actual behavior
Deprecated: strlen(): Passing null to parameter 1 ($string) of type string is deprecated in /project/vendor/drush/drush/src/TestTraits/DrushTestTrait.php on line 79

Workaround
Probably a lazy error_reporting value in php.ini, but I haven't tried it.

System Configuration

Q	A
Drush version?	11.0.5
Drupal version?	9.3.5
PHP version	8.1.2
OS?	Linux