gistfile1.erb

<!-- It is probably easier to read if you initialize item_images to be an empty hash -->
<% @item.item_images ||= Hash.new %>
<% @item.item_images.each do |key, image| %>
  <img src="<%= image.path %>" width="397" <% if key != 0 %>style="display:none"<% end %> />
<% end %>


<!-- Or return a default value for when it is nil -->
<% (@item.item_images || Hash.new).each do |key, image| %>
  <img src="<%= image.path %>" width="397" <% if key != 0 %>style="display:none"<% end %> />
<% end %>