Error 500 when I select the button "Create merge request"

I try to do a merge to master branch and obtain the next result when I select the button “Create merge request”

The error is "ActiveRecord::StatementInvalid (PG::CheckViolation: ERROR: new row for relation “merge_request_diff_commit_users” violates check constraint “merge_request_diff_commit_users_name_or_email_existence”
DETAIL: Failing row contains (1105, null, null).
):
"
What happen in this case? How can I fix this?