Don't render merge checks if no message exists
Currently the merge_checks
component (https://gitlab.com/gitlab-org/gitlab/-/blob/11259c5a0c2415596ad4400bcda7f9d3f26aa89e/app/assets/javascripts/vue_merge_request_widget/components/merge_checks.vue) expects all backend checks to have a message (https://gitlab.com/gitlab-org/gitlab/-/blob/11259c5a0c2415596ad4400bcda7f9d3f26aa89e/app/assets/javascripts/vue_merge_request_widget/components/checks/message.vue#L11) if no message exists on the frontend we will just render an empty row.
We should change the frontend to not render merge checks if the frontend doesn't have a message yet. This way the backend can add the check and then the frontend can do whatever work is needed to get this check to render correctly.
/cc @andr3