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
se = (Series) elSE.get( k );
					if ( seRT == se )
					{
						bFound = true;
						break;
					}
				}
				if ( bFound )
				{
					break;
				}
			}
			if ( !bFound )
			{
				
				
				for ( i = 0; i < axaOrthogonal.length; i++ )
				{
					elSD = axaOrthogonal[i].getSeriesDefinitions( );
					for ( j = 0; j < elSD.size( ); j++ )
					{
						sd = (SeriesDefinition) elSD.get( j );
						elSE = sd.getSeries( );
						for ( k = 0; k < elSE.size( ); k++ )
						{
							se = (Series) elSE.get( k );
							if ( seRT == se )
							{
								bFound = true;
								break;