修复第二个参数为空导致异常

lib/base/webserver/impl/ShelfWebServer.dart

@@ -199,8 +199,13 @@ class ShelfWebServer implements WebServer {
                   print(e);
                 }
               }
-              return im.invoke(v.simpleName,
-                  [req, payload ?? <String, dynamic>{}]).reflectee;
+              List args;
+              if (v.parameters.length == 2) {
+                args = [req, payload ?? <String, dynamic>{}];
+              } else {
+                args = [req];
+              }
+              return im.invoke(v.simpleName, args).reflectee;
             });
           }
         }