My index file : Triing to apply simplify render in views (best practice)

_article.html.erb

<div class="article" data-ref="<%= article.id %>" data-text="<%= article.synopsis? %>" data-video="<%= article.video? %>">
    <div class="img">
        <%= image_tag(article.image.url(:panorama), :class => 'color') %>
    </div>
</div>

index.html.erb

<div id="contenu" class="contenu small">
    <div class="grid inner-contenu">
        <div class="c960">
          <%= render 'article', :collection => @articles %>
        </div>
    </div>
</div>

result

RuntimeError in Articles#index

Showing /Users/stagiaire/Projects/vodmania/app/views/articles/_article.html.erb where line #1 raised:

Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id
Extracted source (around line #1):

1: <div class="article" data-on="false" data-ref="<%= article.id %>" data-text="<%= article.has?(:synopsis) %>" data-video="<%= article.has_video? %>">
2:     <div class="img">
3:         <%= image_tag(article.image.url(:panorama), :class => 'color') %>
4:         <%= image_tag(article.image.url(:panorama_black), :class => 'black') %>
Trace of template inclusion: app/views/articles/index.html.erb

In the index file, replacing render by :

<%= render @articles %>