title: Access to field results in dereference of a null pointer
body: <p>I get this warning when analyzing the code with XCode 4.6 and I don't get it.</p>
  
  <pre><code>    VanishingPointInfo* vpClosestToCenterLine = NULL;
      for (vector&lt;VanishingPointInfo&gt;::iterator vpInfo = lineCrossings.begin(); vpInfo != lineCrossings.end(); vpInfo++)
      {
          if (vpClosestToCenterLine == NULL || vpInfo-&gt;diffToMiddle &lt; vpClosestToCenterLine-&gt;diffToMiddle)
          {
              vpClosestToCenterLine = &amp;(*vpInfo);
          }
      }
  </code></pre>
  
  <p>XCode complains that the access to <code>vpInfo-&gt;diffToMiddle</code> results in a dereference of a <code>NULL</code> pointer. But that is the iterator... </p>