set_relation_n_n is bugged when 5. parameter is a array

I got a problem, i need to put the relation in an_array. But when the 5. parameter was any time in an array, I got below problem:

Severity: Notice
Message: Undefined property: stdClass::$ users_id
Filename: models/Grocery_crud_model.php
Line Number: 345
Backtrace:
File: /var/www/na_project/application/models/Grocery_crud_model.php
Line: 345
Function: _error_handler
File: /var/www/na_project/application/libraries/Grocery_CRUD.php
Line: 1387
Function: get_relation_n_n_selection_array
File: /var/www/na_project/application/libraries/Grocery_CRUD.php
Line: 1378
Function: get_relation_n_n_selection_array
File: /var/www/na_project/application/libraries/Grocery_CRUD.php
Line: 1885
Function: get_edit_values
File: /var/www/na_project/application/libraries/Grocery_CRUD.php
Line: 4575
Function: showEditForm
File: /var/www/na_project/application/controllers/licenses.php
Line: 74
Function: render
File: /var/www/na_project/index.php
Line: 315
Function: require_once

This is my code

foreach($relations_n as $relation_n){
$rel = explode(',' ,$relation_n['relation_n_n']);
$crud->set_relation_n_n($rel[0],$rel[1],$rel[2],$rel[3],$rel[4],$rel[5],$rel[6]);
}

This is inside of $relations_n

Lizenznehmer, licenses_to_user, users, license_id, users_id, username,priority

When im doing this:

foreach($relations_n as $relation_n){
$rel = explode(',' ,$relation_n['relation_n_n']);
$crud->set_relation_n_n($rel[0],$rel[1],$rel[2],$rel[3],'users_id',$rel[5],$rel[6]);
}

Its working perfect.

Does some have any solutions for me or a work around?

sincerly

fapth