Update RecordingCachePool.php (#58)

default second argument changed to empty array in method timeCall, because calling call_user_func_array([$this->cachePool, $name], $arguments); is expecting second argument only Array, not NULL.

src/Cache/RecordingCachePool.php

@@ -57,7 +57,7 @@ protected function addCall($call)
      *
      * @return object
      */
-    private function timeCall($name, array $arguments = null)
+    private function timeCall($name, array $arguments = [])
     {
         $start  = microtime(true);
         $result = call_user_func_array([$this->cachePool, $name], $arguments);