Bug 122850 Table/list should not be able to be inserted in Master Page mode.
Description: Table/list should not be able to be inserted in Master Page mode. Steps to reproduce: 1. New a report and transfer to Master Page mode. 2. New a datasource and dataset 3. Drag a list/table to page header/footer, bind it to dataset and drag some columns inside. 4. Save and preview Expected result: Insert list/table item in master page should be forbidden. Actual result: They are allowed and preview showed "undefine" in page
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
/**
	 * Returns a list of the descendents of this element. The descendents
	 * include elements that directly extend from this one, along with elements
	 * that extend from those, and so on recursively.
	 * <p>
	 * Part of: Inheritance system.
	 * 
	 * @return The list of descendents.
	 */
	public List getDescendents( )
	{
		ArrayList list = new ArrayList( );
		gatherDescendents( list );
		return list;
	}
	/**
	 * Builds up a list of the elements that extend from this one, directly or
	 * indirectly.
	 * <p>
	 * Part of: Inheritance system.
	 * 
	 * @param list
	 *            The list of descendents.
	 */
	public void gatherDescendents( ArrayList list )
	{
		if ( derived == null )
			return;
		for ( int i = 0; i < derived.size( ); i++ )
		{