Bug 118738 can't preview meter chart with grouping
Try to preview the following report with a meter chart group on the Y series, it fails. It used to work before, this is a regression. An exception is thrown org.eclipse.birt.chart.exception.ChartException: Can not plot meter series with null or non-numeric datapoint. at org.eclipse.birt.chart.render.DialRenderer.<init>(DialRenderer.java:132) at org.eclipse.birt.chart.render.Dial.compute(Dial.java:98) at org.eclipse.birt.chart.factory.Generator.build(Generator.java:759)
chart/org.eclipse.birt.chart.device.extension/src/org/eclipse/birt/chart/device/image/JavaxImageIOWriter.java
if ( (int) _bo.getWidth( ) <= 0 || (int) _bo.getHeight( ) <= 0 )
			{
				throw new ChartException( ChartDeviceExtensionPlugin.ID,
						ChartException.INVALID_IMAGE_SIZE,
						"exception.invalid.image.size", 
						ResourceBundle.getBundle( Messages.DEVICE_EXTENSION,
								getLocale( ) ) );
			}
			
			_img = new BufferedImage( (int) _bo.getWidth( ),
					(int) _bo.getHeight( ),
					getImageType( ) );
		}
		super.setProperty( IDeviceRenderer.GRAPHICS_CONTEXT, _img.getGraphics( ) );
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.chart.device.IDeviceRenderer#after()
	 */
	public void after( ) throws ChartException
	{
		super.after( );
		
		Iterator it = null;
		String s = getFormat( );
		if ( s != null )
		{
			it = ImageIO.getImageWritersByFormatName( s );
			if ( !it.hasNext( ) )