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/command/ContentCommand.java
*             the slot cannot contain the given element.
	 */
	private void checkContainmentContext( int slotId, DesignElement content )
			throws NameException, ContentException
	{
		List errors = element.checkContainmentContext( module, slotId, content );
		if ( !errors.isEmpty( ) )
		{
			SemanticException e = (SemanticException) errors.get( 0 );
			assert e instanceof NameException || e instanceof ContentException;
			if ( e instanceof NameException )
				throw (NameException) e;
			if ( e instanceof ContentException )
				throw (ContentException) e;
		}
	}
	/**
	 * Adds the element name and names of nested element in it to name spaces.
	 * 
	 * @param content
	 *            the content to add
	 * @throws NameException
	 *             if any element has duplicate name with elements already on
	 *             the design tree.
	 */
	private void addElementNames( DesignElement content ) throws NameException
	{
		
		
		assert content.getContainer( ) != null;