code>t</code>
 until the unwrapping encounters an Object whose
 <code>getClass()</code> is not equal to
 <code>FacesException.class</code> or
 <code>javax.el.ELException.class</code>.  If there is no root cause, <code>null</code> is returned.</p></div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>t</code> - passed-in wrapped <code>Throwable</code>.</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>unwrapped object.</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><