fix(agent): 修复消息气泡卡片数据可能为null时的处理

添加对卡片数据可能为null的检查，并为各类型卡片提供默认值以避免空指针异常

lib/modules/agent/views/message_bubble.dart

@@ -233,29 +233,33 @@ class MessageBubble extends GetView<AgentController> {
       // 判断消息类型，显示不同的卡片
       if (meta!.keys.contains('music_play')) {
         final card_music =
-            meta!["music_play"]['card_music'] as Map<String, dynamic>;
+            meta!["music_play"]['card_music'] as Map<String, dynamic>?;
-        final musicId = card_music!['id'];
+        if (card_music != null) {
-        final musicName = card_music!['name'] as String;
+          final musicId = card_music['id'];
-        final musicUrl = card_music!['url'] as String;
+          final musicName = card_music['name'] as String? ?? '未知歌曲';
-        final musicSinger = card_music!['sgener'] as String;
+          final musicUrl = card_music['url'] as String? ?? '';
-        final musicImage = card_music!['image'] as String;
+          final musicSinger = card_music['sgener'] as String? ?? '未知歌手';
+          final musicImage = card_music['image'] as String? ?? '';
           //音乐卡片
           return buildMusicItem(
               context, musicId, musicName, musicUrl, musicSinger, musicImage);
+        }
       } else if (meta!.keys.contains('music_playlist')) {
         final card_musiclist =
-            meta!["music_playlist"]['card_musiclist'] as Map<String, dynamic>;
+            meta!["music_playlist"]['card_musiclist'] as Map<String, dynamic>?;
-        final rawList = card_musiclist['musics'] as List;
+        if (card_musiclist != null) {
+          final rawList = card_musiclist['musics'] as List? ?? [];
           final playlist =
               rawList.map((e) => Map<String, dynamic>.from(e)).toList();
           //音乐播放列表
           return buildMusicContent(context, playlist);
+        }
       } else if (meta!.keys.contains('maps_weather')) {
-        final city = meta!['maps_weather']['city'] as String;
+        final city = meta!['maps_weather']['city'] as String? ?? '未知城市';
-        final rawList = meta!['maps_weather']['forecasts'] as List;
+        final rawList = meta!['maps_weather']['forecasts'] as List? ?? [];
         final daylist =
             rawList.map((e) => Map<String, dynamic>.from(e)).toList();
-        final now = daylist[0] as Map<String, dynamic>;
+        final now = daylist.isNotEmpty ? daylist[0] : <String, dynamic>{};
         //天气
         return buildWeatherContent(
           context,
@@ -264,18 +268,19 @@ class MessageBubble extends GetView<AgentController> {
           daylist,
         );
       } else if (meta!.keys.contains('card_travel')) {
-        final rawList = meta!['card_travel']['items'] as List;
+        final rawList = meta!['card_travel']['items'] as List? ?? [];
         final travellist =
             rawList.map((e) => Map<String, dynamic>.from(e)).toList();
         // 旅游
         return buildTravelContent(context, travellist);
       } else if (meta!.keys.contains('maps_route_navigation')) {
         final card_navigation = meta!['maps_route_navigation']
-            ['card_navigation'] as Map<String, dynamic>;
+            ['card_navigation'] as Map<String, dynamic>?;
-        final start = card_navigation['start'] as String;
+        if (card_navigation != null) {
-        final end = card_navigation['end'] as String;
+          final start = card_navigation['start'] as String? ?? '';
-        final destination = card_navigation['destination'] as String;
+          final end = card_navigation['end'] as String? ?? '';
-        final rawList = card_navigation['items'] as List;
+          final destination = card_navigation['destination'] as String? ?? '';
+          final rawList = card_navigation['items'] as List? ?? [];
           final list = rawList.map((e) => Map<String, dynamic>.from(e)).toList();
           final rawNavigation = card_navigation['navigation'];
           final Map<String, dynamic>? navigation =
@@ -289,6 +294,7 @@ class MessageBubble extends GetView<AgentController> {
               modes: list,
               navigation: navigation);
         }
+      }
 
       // if (message.contains('播放列表') || message.contains('音乐')) {
       //   return _buildMusicContent(context);