Bug 124777 Set blank tooltip in chart title will cause exception when preview.
Description: Set blank tooltip in chart title will cause exception when preview. Steps to reproduce: 1. New a simple chart 2. Add title interactivity: mouse over/show tooltip, keep tooltip text blank and click Add button. 3. Preview the chart in viewer and move mouse over the chart title. Expected result: Nothing happen. Actual result: Unexpected exception dialog poped up.
chart/org.eclipse.birt.chart.device.svg/src/org/eclipse/birt/chart/device/svg/SVGRendererImpl.java
writeDocumentToOutputStream( dom,
						(OutputStream) oOutputIdentifier );
			}
			catch ( Exception ex )
			{
				throw new ChartException( ChartDeviceSVGPlugin.ID,
						ChartException.RENDERING,
						ex );
			}
		}
		else if ( oOutputIdentifier instanceof String )
		{
			FileOutputStream fos = null;
			try
			{
				fos = new FileOutputStream( (String) oOutputIdentifier );
				writeDocumentToOutputStream( dom, fos );
				fos.close( );
			}
			catch ( Exception ex )
			{
				throw new ChartException( ChartDeviceSVGPlugin.ID,
						ChartException.RENDERING,
						ex );
			}
		}
		else
		{
			throw new ChartException( ChartDeviceSVGPlugin.ID,
					ChartException.RENDERING,