fix ios issue

ios/Classes/FlutterUmengPlugin.swift

@@ -19,6 +19,7 @@ public class FlutterUmengPlugin: NSObject, FlutterPlugin {
     default:
       result(FlutterMethodNotImplemented)
     }
+    result(true)
   }
 
   // 初始化

pubspec.yaml

@@ -1,6 +1,6 @@
 name: flutter_umeng
 description: "友盟flutter插件"
-version: 0.0.2
+version: 0.0.3
 homepage: http://git.atmob.com:28999/Atmob-Flutter/flutter_umeng.git
 
 environment: