Update Foundation.php

Author: Hanson

src/Foundation.php

@@ -102,7 +102,7 @@ public function setConfig(array $config)
 
     public function getConfig($key = null)
     {
-        return $key ? $this->config[$key] : $this->config;
+        return $key ? ($this->config[$key] ?? null) : $this->config;
     }
 
     /**
@@ -127,4 +127,4 @@ public function __set($id, $value)
     {
         $this->offsetSet($id, $value);
     }
-}
+}