修复了可以重复结项的BUG

src/main/java/cn/edu/hfut/rmdjzz/projectmanagement/service/impl/ProjectServiceImpl.java

@@ -56,6 +56,8 @@ public class ProjectServiceImpl extends ServiceImpl<ProjectMapper, Project> impl
             throw new BadRequestException("项目不存在");
         if(!Objects.equals(staffId, targetProject.getProjectCreator()))
             throw new BadRequestException("用户请求非法");
+        if(targetProject.getIsCompleted())
+            throw new BadRequestException("该项目已结项");
         targetProject.setIsCompleted(true);
         targetProject.setProjectCloseTime(LocalDate.now());
         if(baseMapper.updateById(targetProject)==1)