title: "No relation" in cypher query
body: <p>How is it possible in cypher to have a query like: 
  "return all people that anna follows that don't follow anyone"?</p>
  
  <p>In the following (where I have the id of the start node made clear after the query) the "r is null"-part does not seem to work:</p>
  
  <pre><code>START o=node({id}) 
  MATCH (a)-[:follows]-&gt;(b)-[r]-&gt;(c) 
  WHERE a.name="anna" and r is null 
  RETURN b
  </code></pre>
  
  <p>Right now, "follows" is the only relation I have. 
  But also </p>
  
  <pre><code>START o=node({id}) 
  MATCH (a)-[:follows]-&gt;(b)-[:follows]-&gt;(c)
  WHERE a.name="anna" and c is null
  RETURN b* does not work.
  </code></pre>
  
  <p>By doesn't work I mean: I don't get any results although there should be some. </p>