fix sonar A "NullPointerException" could be thrown

xueyi-modules/xueyi-nlt/src/main/java/com/xueyi/nlt/nlt/controller/DmIntentController.java

@@ -495,10 +495,10 @@ public class DmIntentController extends BaseController<DmIntentQuery, DmIntentDt
         // 从列表中获取知识库任务
         TaskKnowledgeVo vo = (TaskKnowledgeVo) redisTemplate2.opsForList().leftPop("group:task");
 
-        log.info("从缓存中获取对象：{}",vo.toString());
         if (vo == null) {
             return R.ok(null,"没有任务");
         }
+        log.info("从缓存中获取对象：{}",vo.toString());
 
         if (vo.getSplit() != SYS_DICT_DATA_SPLITED) {
             // 请开始你的表演