@collection is always available when card scoped

app/views/cards/assignments/new.html.erb

@@ -2,7 +2,7 @@
   <strong class="popup__title margin-block-start-half pad-inline-half txt-nowrap">Assign this to…</strong>
 
   <div class="flex flex-column full-width popup__list">
-    <% @card.collection.users.active.alphabetically.each do |user| %>
+    <% @collection.users.active.alphabetically.each do |user| %>
         <%= button_to card_assignments_path(@card, params: { assignee_id: user.id }), method: :post, class: "btn popup__item full-width" do %>
           <span class="overflow-ellipsis"><%= user.name %></span>
           <%= icon_tag "check", size: 18, class: "checked flex-item-justify-end" if @card.assignees.include?(user) %>