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
* 
	 * @param module
	 *            the module
	 * @param propName
	 *            the name of the property
	 * @return <code>true</code> if the property is resolved;
	 *         <code>false</code> otherwise.
	 */
	public boolean checkElementReference( Module module, String propName )
	{
		assert !StringUtil.isBlank( propName );
		
		Object value = propValues.get( propName );
		if ( value == null )
			return true;
		
		ElementPropertyDefn prop = getPropertyDefn( propName );
		assert PropertyType.ELEMENT_REF_TYPE == prop.getTypeCode( );
		
		ElementRefValue ref = resolveElementReference( module, prop );
		return ref.isResolved( );
	}
	/**
	 * Returns the list of elements that extend this one.
	 * 
	 * @return the list of elements. The list is always non-null.
	 */
	public List getDerived( )
	{
		if ( derived != null )