Fix error during handling of closure errors

[mikehaertl]

Q	A
Is bugfix?	yes
New feature?	no
Breaks BC?	no
Tests pass?	-
Fixed issues	#13689

If an error occurs inside a closure method, the error handler will fail. For example:

        $x = array_map(function ($r) {
            return $r->doesnotexist;
        }, [1, 2, 3]);

Will lead to:

An Error occurred while handling another error:
ReflectionException: Method app\controllers\ClientController::app\controllers{closure}() does not exist in /var/www/vendor/yiisoft/yii2/web/ErrorHandler.php:199

The fix is easy, but I was not sure how to properly test this.

[samdark]

Fixed in 6792099