One of parameters (value: ) is not of the type CommaSeparatedIntegers for lesser-permissioned users
I'm not sure all of the variations where you can get this but a simple one is:
cv ev "civicrm_api3('Relationship', 'create', ['contact_id_a' => 8, 'contact_id_b' => 9, 'relationship_type_id' => 'Sibling of']);"
where 8 and 9 are suitable individual contacts. It actually happens during the CRM_Utils_Recent:add()
call that comes after not the relationship creation.
It's from here and it's because it assumes that the earlier query will find at least one row and populate $ids
: https://github.com/civicrm/civicrm-core/pull/26041/files#diff-7fd1affe37f9de9a37acf9decf9cecb5433999cf097eccda8b1f2af2286c32e3R268
It seems like that wouldn't be limited to just the above scenario.
Came up in weekly webform test runs.