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
}
						}
						if ( bFound )
						{
							break;
						}
					}
					if ( bFound )
					{
						break;
					}
				}
			}
			if ( !bFound )
			{
				throw new ChartException( ChartDeviceExtensionPlugin.ID,
						ChartException.OUT_OF_SYNC,
						"info.cannot.find.series", 
						new Object[]{
							seRT
						},
						ResourceBundle.getBundle( Messages.DEVICE_EXTENSION,
								getLocale() ) );
			}
			
			
			axaBase = cwaDT.getPrimaryBaseAxes( );
			axBase = axaBase[0];
			axaOrthogonal = cwaDT.getOrthogonalAxes( axBase, true );
			if ( i == -1 )