Bug 199714 NPE with invalid url[0002]
viewer/org.eclipse.birt.report.viewer/birt/WEB-INF/classes/org/eclipse/birt/report/context/ViewerAttributeBean.java
else
		{
			
			try
			{
				if ( !designFile.startsWith( "/" ) ) 
					designFile = "/" + designFile; 
				URL url = request.getSession( ).getServletContext( )
						.getResource( designFile );
				if ( url != null )
					return url.openConnection( ).getLastModified( );
			}
			catch ( Exception e )
			{
			}
		}
		return -1L;
	}
	/**
	 * Get report service instance.
	 */
	protected IViewerReportService getReportService( )
	{
		return BirtReportServiceFactory.getReportService( );
	}
	/**
	 * Clear our resources.
	 * 
	 * @exception Throwable
	 * @return