Null exception when trying to use a list
<p>I have StartingMap that inherits from Map. Here is what I am trying to do:</p>

<pre><code>Map m_map;
List&lt;Map&gt; m_versions;

m_versions.add(new StartingMap(...)); // create null reference exeption

m_map= new StartingMap(...); // no error and load the map perfectly
</code></pre>

<p>Why do I get an error with the first one and not the second one ? I am doing the same thing.</p>
