plugin_framework, debug

Signed-off-by: fufesou <shuanglongchen@yeah.net>

flutter/lib/plugin/event.dart

@@ -1,11 +1,19 @@
+import 'dart:convert';
+import 'package:flutter/material.dart';
+
 void handlePluginEvent(
   Map<String, dynamic> evt,
   String peer,
   Function(Map<String, dynamic> e) handleMsgBox,
 ) {
-  if (evt['content']?['c'] == null) return;
-  final t = evt['content']?['t'];
-  if (t == 'MsgBox') {
-    handleMsgBox(evt['content']?['c']);
+  Map<String, dynamic>? content;
+  try {
+    content = json.decode(evt['content']);
+  } catch (e) {
+    debugPrint(
+        'Json decode plugin event content failed: $e, ${evt['content']}');
+  }
+  if (content?['t'] == 'MsgBox') {
+    handleMsgBox(content?['c']);
   }
 }