title: Automapper returning an empty collection, I want a null
body: <pre><code>public class Person
  {
     Name { get; set; }
     IEnumerable&lt;Address&gt; Addresses { get; set; }
  }
  
  public class PersonModel
  {
     Name { get; set; }
     IEnumerable&lt;AddressModel&gt; Addresses { get; set; }
  }
  </code></pre>
  
  <p>If I map <code>Person</code> to <code>PersonModel</code> like so:</p>
  
  <pre><code>Mapper.DynamicMap&lt;Person, PersonModel&gt;(person);
  </code></pre>
  
  <p>If the <code>Addresses</code> property on <code>Person</code> is null they are mapped on <code>PersonModel</code> as an empty <code>Enumerable</code> instead of null.</p>
  
  <p>How do I get <code>PersonModel</code> to have null <code>Addresses</code> instead of an empty <code>Enumerable</code>?</p>