title: django no reverse match error but i have optional view parameters
body: <p>I have the following link that is getting a "no reverse match" error:</p>
  
  <pre><code>&lt;a href="{% url 'journals:entry' action='add'  day_number=journal.day_number  %}" &gt;
  </code></pre>
  
  <p>My url looks like this:</p>
  
  <pre><code>url(r'^day/(?P&lt;day_number&gt;\d+)/(?P&lt;action&gt;add|edit|delete)/(?P&lt;pk&gt;\d+)/$', views.entry, name='entry'),
  </code></pre>
  
  <p>My view looks like this:</p>
  
  <pre><code>def entry(request, day_number=0, pk=None, action='add'):
  </code></pre>
  
  <p>I don't have a pk but I thought I don't need one since this param is optional.</p>
  
  <p>What am I doing wrong?</p>