Fix problem of stack horizontal without image (#48)

Author: fblupi

app/cells/decidim/alternative_landing/content_blocks/stack_horizontal/show.erb

@@ -8,7 +8,7 @@
     <% 1.upto(3) do |item_number| %>
       <div class="stack-item">
         <div class="stack-image">
-          <%= image_tag image(item_number) %>
+          <%= image_tag image(item_number) if image(item_number).present? %>
         </div>
         <div class="stack-body">
           <div>

spec/shared/system_homepage_examples.rb

@@ -19,7 +19,7 @@
             # /rails/active_storage/representation/redirect/same-hash--different-token/same-file-name
             # That's why we are splitting by "--" and comparing the first
             img_path = content_block.images_container.attached_uploader("image_#{item_number}".to_sym).path(variant: :landscape)
-            [img_path.split("--").first, img_path.split("/").last].each do |regex|
+            img_path && [img_path.split("--").first, img_path.split("/").last].each do |regex|
               expect(page.find("img")[:src]).to match(/#{regex}/)
             end
           end

spec/system/homepage_spec.rb

@@ -51,6 +51,16 @@
     describe "stack blocks" do
       it_behaves_like "render all stack block elements", "stack-horizontal"
       it_behaves_like "render all stack block elements", "stack-vertical"
+
+      context "without images" do
+        before do
+          stack_horizontal_block.attachments.destroy_all
+          stack_vertical_block.attachments.destroy_all
+        end
+
+        it_behaves_like "render all stack block elements", "stack-horizontal"
+        it_behaves_like "render all stack block elements", "stack-vertical"
+      end
     end
 
     describe "tiles block" do