Suggested approvers can be nil when creating a MR

https://sentry.gitlap.com/gitlab/gitlabcom/issues/7747/

NoMethodError: undefined method `any?' for nil:NilClass
  app/views/shared/issuable/_form.html.haml:160:in `_app_views_shared_issuable__form_html_haml___226160332588378899_70076431301820'
    - if @suggested_approvers.any?
  app/views/projects/merge_requests/_form.html.haml:2:in `block in _app_views_projects_merge_requests__form_html_haml___169311772788873509_70076431181520'
    = render 'shared/issuable/form', f: f, issuable: @merge_request
  app/views/projects/merge_requests/_form.html.haml:1:in `_app_views_projects_merge_requests__form_html_haml___169311772788873509_70076431181520'
    = form_for [@project.namespace.becomes(Namespace), @project, @merge_request], html: { class: 'merge-request-form form-horizontal common-note-form js-requires-input js-quick-submit' } do |f|
  app/views/projects/merge_requests/edit.html.haml:6:in `_app_views_projects_merge_requests_edit_html_haml___1081790648545913074_70076430875640'
    = render 'form'
  app/controllers/projects/merge_requests_controller.rb:178:in `update'
    render "edit"
...
(172 additional frame(s) were not displayed)

ActionView::Template::Error: undefined method `any?' for nil:NilClass
  app/views/shared/issuable/_form.html.haml:160:in `_app_views_shared_issuable__form_html_haml___226160332588378899_70076431301820'
    - if @suggested_approvers.any?
  app/views/projects/merge_requests/_form.html.haml:2:in `block in _app_views_projects_merge_requests__form_html_haml___169311772788873509_70076431181520'
    = render 'shared/issuable/form', f: f, issuable: @merge_request
  app/views/projects/merge_requests/_form.html.haml:1:in `_app_views_projects_merge_requests__form_html_haml___169311772788873509_70076431181520'
    = form_for [@project.namespace.becomes(Namespace), @project, @merge_request], html: { class: 'merge-request-form form-horizontal common-note-form js-requires-input js-quick-submit' } do |f|
  app/views/projects/merge_requests/edit.html.haml:6:in `_app_views_projects_merge_requests_edit_html_haml___1081790648545913074_70076430875640'
    = render 'form'
  app/controllers/projects/merge_requests_controller.rb:178:in `update'
    render "edit"
...
(172 additional frame(s) were not displayed)

Reassigned to @smcgivern

This was two issues combining:

1. https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/470 didn't apply the same coercion of the approvals_before_merge param to editing an existing MR as there was for creating a new MR. This meant that creating a new MR with the same number of approvers as the target project, editing it, not changing anything, and clicking Save would produce a validation error.
2. set_suggested_approvers wasn't called in a couple of places where we render the MR edit form (like the above).

This issue was affecting us after updating to 8.9.0-ee docker version this morning. Developers were unable to create merge requests with or without specifying approvers.

Applying the proposed patches fixed it for us.

Status changed to closed by commit gitlab-org/gitlab-ee@9525c1d67c3ecbf2264f61ee391b7de96d5846da

mentioned in issue #18978 (closed)

mentioned in merge request !14785