Empty phone number fields cause exception in Craft CMS 5.9.12

[thasmo]

craft\helpers\StringHelper::stripWhitespace(): Argument #1 ($str) must be of type string, null given, called in /var/www/html/vendor/presseddigital/linkit/src/models/Phone.php on line 35

$this->value seems to be null for some reason. I assume this value was an empty string in prior Craft CMS versions, or something.

This might be an unintended BC break in Craft 5.9 after all, maybe.