接口请求签名时，过滤掉参数数组里值为null的key

@@ -49,6 +49,7 @@ class Sign
      */
     public static function getSign(array $package)
     {
+        $package = array_filter($package, function($val){return !is_null($val);});
         $package = self::packageSort($package);
         return self::makeSign($package);
     }