修改删除展板出现得bug

src/main/java/cn/chnmuseum/party/web/controller/ExhibitionBoardController.java

@@ -620,9 +620,9 @@ public class ExhibitionBoardController extends BaseController {
             queryWrapper.eq(LearningContentBoard::getExhibitionBoardId, id);
             queryWrapper.select(LearningContentBoard::getLearningContentId);
             List<String> list = this.learningContentBoardService.listObjs(queryWrapper, Object::toString);
-            List<LearningContent> learningContents = this.learningContentService.listByIds(list);
-            String collect = learningContents.stream().map(LearningContent::getName).collect(Collectors.joining(","));
             if (CollectionUtil.isNotEmpty(list)) {
+                List<LearningContent> learningContents = this.learningContentService.listByIds(list);
+                String collect = learningContents.stream().map(LearningContent::getName).collect(Collectors.joining(","));
                 return getFailResult("该展板被学习内容:" + collect + "使用，不能被删除！");
             }
         }