[bugfix] can not read the last sentence

lib/services/chat_sse_service.dart

@@ -114,7 +114,7 @@ class ChatSseService {
           if (line.startsWith('data:')) {
             final jsonStr = line.substring(5).trim();
             if (jsonStr == '[DONE]' || jsonStr.contains('message_end')) {
-              await processBuffer(isChinese);
+              TtsUtil.complete();
               onStreamResponse(messageId, responseText, true);
               break;
             }