title: rich:calendar defaultLabel attribute causes conversion error
body: <p>Using the defaultLabel attribute of the Rich Faces Calendar component correctly displays the reminder text for the date format like I would like it to.  However, when this reminder text is on an optional field, then a conversion error occurs as if it was trying to convert the reminder text into a date.</p>
  
  <pre><code>&lt;rich:calendar enableManualInput="true" value="#{participantSummaryManagedBean.dob}"
      id="dob" locale="US" popup="true" datePattern="MMddyyyy" defaultLabel="MMDDYYYY"
      showApplyButton="false" converterMessage="Use MMDDYYYY format"&gt;
  &lt;/rich:calendar&gt;
  </code></pre>
  
  <p>Confirmed in RichFaces versions 4.2.2.Final, 4.2.3.Final, and 4.3.0.20121024-M2</p>
  
  <p>Is there a way to prevent or get around this?</p>