Bug 116180 [SPM]Dataset can not be previewed in report designer on Mac
Description: Pull a dataset into the layout, preview in designer there is anothing displayed. Steps: 1, Create a sample datasource. create a dataset with sql statement "select * from CLASSICMODELS.EMPLOYEES" 2, Pull the dataset to the layout of the designer. 3, Preview, there is nothing displayed.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/internal/ui/dnd/DesignElementDragAdapter.java
* Constructor
	 * 
	 * @param viewer
	 */
	public DesignElementDragAdapter( StructuredViewer viewer )
	{
		super( );
		this.viewer = viewer;
	}
	/**
	 * @see DragSourceAdapter#dragFinished(DragSourceEvent)
	 */
	public void dragFinished( DragSourceEvent event )
	{
		if ( event.doit )
		{
			TemplateTransfer.getInstance( ).setTemplate( null );
			if ( Policy.TRACING_DND_DRAG )
			{
				System.out.println( "DND >> Drag finished." ); 
			}
		}
	}
	/**
	 * @see DragSourceAdapter#dragSetData(DragSourceEvent)
	 */
	public void dragSetData( DragSourceEvent event )
	{
		IStructuredSelection selection = (IStructuredSelection) getViewer( ).getSelection( );
		Object[] objects = selection.toList( ).toArray( );