Database error when creating membership between user and group

Camunda 7 Topics Discussion & Questions
1

I am trying to add userId and adding groups to process engine after fetching from header in REST API.

Code for creating user and group membership


private void setGroupMembership(String userId, IdentityService identityService) throws Exception{ // throws AuthenticationException

        /* When uncommented: Exception: User already exist
        User user = identityService.newUser(userId);
        identityService.saveUser(user);
        */

        if (groupIds.isEmpty()) {
            throw new Exception("Group Id is null");
        }

        for (String groupId: groupIds) {
 

            /* When uncommented: Exception: Group already exist
            Group group = identityService.newGroup(groupId);
            identityService.saveGroup(group);
            */

            // create membership
            identityService.createMembership(userId, groupId);
        }

    }

I am getting the following error when I try to open Camunda Webapp

org.camunda.bpm.engine.ProcessEngineException: ENGINE-03083 Unexpected exception while executing database 
### Error updating database.  Cause: java.lang.NullPointerException
### The error may involve org.camunda.bpm.engine.impl.persistence.entity.MembershipRelation.insertMembership-Inline
### The error occurred while setting parameters
### SQL: insert into ACT_ID_MEMBERSHIP (USER_ID_, GROUP_ID_)     values (       ?,       ?     )
### Cause: java.lang.NullPointerException