don't allow edits to adjustments for canceled orders

app/views/spree/admin/adjustments/_adjustments_table.html.haml

@@ -17,6 +17,7 @@
         %td.align-center.label= adjustment.label
         %td.align-center.amount= adjustment.display_amount.to_html
         %td.align-center.included-tax= adjustment.display_included_tax.to_html
-        %td.actions
-          = link_to_edit adjustment, no_text: true
-          = link_to_delete adjustment, no_text: true
+        - unless @order.canceled?
+          %td.actions
+            = link_to_edit adjustment, no_text: true
+            = link_to_delete adjustment, no_text: true

spec/features/admin/adjustments_spec.rb

@@ -87,4 +87,17 @@ feature '
     expect(page).to have_selector 'td.amount', text: '110'
     expect(page).to have_selector 'td.included-tax', text: '10'
   end
+
+  scenario "viewing adjustments on a canceled order" do
+    # Given a taxed adjustment
+    adjustment = create(:adjustment, label: "Extra Adjustment", adjustable: order,
+                        amount: 110, included_tax: 10, order: order)
+    order.cancel!
+
+    login_as_admin_and_visit spree.edit_admin_order_path(order)
+
+    click_link 'Adjustments'
+
+    expect(page).to_not have_selector('tr a.icon-edit')
+  end
 end