Merge pull request #200 from maff/php7.2-count-routers

PHP 7.2 compatibility: check if sortedRouters is null before trying to count it

Author: dbu

src/ChainRouter.php

@@ -47,7 +47,7 @@ class ChainRouter implements ChainRouterInterface, WarmableInterface
     /**
      * @var RouterInterface[] Array of routers, sorted by priority
      */
-    private $sortedRouters;
+    private $sortedRouters = [];
 
     /**
      * @var RouteCollection