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
if ( oldRef != null )
		{
			target = oldRef.getTargetElement( );
			if ( target != null )
				target.dropClient( this );
		}
		
		
		
		if ( newRef != null )
		{
			target = newRef.getTargetElement( );
			if ( target != null )
				target.addClient( this, prop.getName( ) );
		}
	}
	/**
	 * Implements to cache a back-pointer from a referenced structure. This
	 * element has a structure reference property that can point to another
	 * "referencable" structure. To maintain semantic consistency, the
	 * referenced structure maintains a list of "clients" that identifies the
	 * elements that refer to it. The client list is used when the target
	 * structure changes names or is deleted. In these cases, the change
	 * automatically updates the clients as well.
	 * <p>
	 * References can be in two states: resovled and unresolved. An unresolved
	 * reference is just a name, but the system has not yet identified the
	 * target structure, or if a target even exists. A resolved reference caches