app/views/leagues/matches/_round_fields.html.haml
%li.list-group-item.nested-fields
= f.collection_select :map_id, league.map_pool, :id, :name,
label_class: 'mr-3', wrapper: { class: 'mr-3 mb-0' }
= link_to_remove_association f, class: 'btn btn-danger' do
= inline_svg_tag 'open_iconic/trash.svg', class: 'icon'