URIElement siteaccess matcher passes wrong value when setting value > 1

It has been verified that the URIElement siteaccess matcher passes a wrong value when the setting value defined in ezpublish.yml is grater than 1.

Ref: https://doc.ez.no/display/EZP/Siteaccess+Matching#SiteaccessMatching-Availablematchers

Steps to reproduce:

1. Prepare a test eZ Publish 5.4 installation, fully updated to 5.4.5;
2. Edit ezpublish/config/ezpublish.yml, and set the URIElement matcher to a value greater than 1:

ezpublish:
    siteaccess:
        ...
        match:
            URIElement: '2'

3. Edit /vendor/ezsystems/ezpublish-kernel/eZ/Publish/Core/MVC/Symfony/SiteAccess/Matcher/URIElement.php and add the following debug code:

public function __construct($elementNumber)
{
    var_dump( (int)$elementNumber );
    $this->elementNumber = (int)$elementNumber;
}

4. Visit a siteaccess. A "int(2)" debug message would be expected, instead "int(1)" is displayed.