add socket check

src/Xash3D/Master.php

@@ -41,11 +41,14 @@ class Master
     }
 
     public function __destruct()
+    {
+        if (true === is_resource($this->_socket))
         {
             fclose(
                 $this->_socket
             );
         }
+    }
 
     public function getServersIPv6(
         int    $limit   = 100,