Bug 145520 Group name will not show up in group list if the group use default name and key expression has no value
Description: Group name will not show up in group list if key expression has no value. Steps to reproduce: 1. Insert a table into report, bind it to a data set 2. Switch to property editor -> groups 3. Click on add button to open new group dialog, then press ok button Expected result: A new group with default name will be added to group list Actual result: A new group is added to group list, but without group name. But when let group tab lost focus and get focus again, you can see the group name.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/Module.java
* Removes one validation listener. If the listener not registered, then the
	 * request is silently ignored.
	 * 
	 * @param listener
	 *            the validation listener to remove
	 * @return <code>true</code> if <code>listener</code> is sucessfully
	 *         removed. Otherwise <code>false</code>.
	 * 
	 */
	public boolean removeValidationListener( IValidationListener listener )
	{
		if ( validationListeners == null )
			return false;
		return validationListeners.remove( listener );
	}
	/**
	 * Broadcasts the validation event to validation listeners.
	 * 
	 * @param element
	 *            the validated element
	 * @param event
	 *            the validation event
	 */
	public void broadcastValidationEvent( DesignElement element,
			ValidationEvent event )
	{
		if ( validationListeners != null )
		{
			Iterator iter = validationListeners.iterator( );
			while ( iter.hasNext( ) )