update

mec-biz/src/main/java/com/ym/mec/biz/service/impl/ClassGroupServiceImpl.java

@@ -157,13 +157,13 @@ public class ClassGroupServiceImpl extends BaseServiceImpl<Integer, ClassGroup>
 			throw new BizException("课程组类型不能为空");
 		}
         String userIds = classGroup.getUserIds();
+
+        Set<String> userIdStrSet = new HashSet<String>();
         
-        if(StringUtils.isBlank(userIds)){
-        	userIds = "";
+        if(StringUtils.isNotBlank(userIds)){
+        	userIdStrSet = new HashSet<>(Arrays.asList(userIds.split(",")));
         }
 
-        Set<String> userIdStrSet = new HashSet<>(Arrays.asList(userIds.split(",")));
-
         Date date = new Date();
         classGroup.setCreateTime(date);
         classGroup.setUpdateTime(date);