Bug 122045 Template should show blank preview when there is no image
Create a template but do not associate an image with it. Place the template in the templates directory. Now, create a new report design. On the second page of the New Report dialog, select the template that has no image. Actual result: The preview appears as a white rectangle with a small red square in the top left. Expected result: The preview appears as a gray background in the preview image area.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/internal/ui/wizards/WizardTemplateChoicePage.java
templateList.addListener( SWT.Selection, templateListener );
	}
	private Listener templateListener = new Listener( ) {
		public void handleEvent( Event event )
		{
			
			selectedIndex = templateList.getSelectionIndex( );
			description.setText( ( (Template) templates.get( selectedIndex ) )
					.getTemplateDescription( ) );
			
			previewPane.layout( );
			String key = ( (Template) templates.get( selectedIndex ) )
					.getPicturePath( );
			Object img = imageMap.get( key );
			if ( img == null )
			{
				img = ReportPlugin.getImage( key );
				imageMap.put( key, img );
			}
			previewCanvas.clear( );
			previewCanvas.loadImage( ( (Image) img ) );
			previewCanvas.showOriginal( );
			chkBox.setEnabled( !( (Template) templates.get( selectedIndex ) )
					.getCheatSheetId( ).equals( "" ) ); 
		}
	};
	/**
	 * @return Returns the templates of selected item.
	 */
	public Template getTemplate( )