title: Ramda filter null prop
body: <p>I have array of event objects, looks like:</p>
  
  <pre><code>{
      date: "2015-06-03T19:29:01.000Z",
      description: "Test",
      talks: [{
          author: "Nick",
          tags: ["tag1", "tag2", "tag3"]
      }]
  } 
  </code></pre>
  
  <p>I want to take only tags from this object, so I use Ramda like this:</p>
  
  <pre><code>let eventTags = pipe(prop('talks'), map(prop('tags')), flatten, uniq)
  ... 
  eventTags(event); //and call function on event object
  </code></pre>
  
  <p>But there is cases when event object looks like this:</p>
  
  <pre><code>{
      date: "2015-06-03T19:29:01.000Z",
      description: "Test",
      talks: [{
          author: "Nick",
          tags: null
      }]
  } 
  </code></pre>
  
  <p>So I got <code>[null]</code> in my <code>eventTags</code> array, but I want to get an empty array instead. So how can I filter null?</p>