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
}
					components.add(idTemp);
					
					
					Element primGroup = svg_g2d.createElement("g"); 
					svg_g2d.pushParent(primGroup);
					primGroup
							.setAttribute("id", seDT.hashCode() + "_" + idTemp); 
					primGroup.setAttribute("style", "visibility:visible;"); 
					if (!drawText)
						svg_g2d.setDeferStrokColor(primGroup);
				} catch (ChartException e) {
					logger.log(e);
					return;
				}
			}
		}
	}
	
	/**
	 * UnGroups the svg drawing instructions that represents this primitive events. 
	 * 
	 * @param pre primitive render event
	 * @param drawText TODO
	 */
	protected void ungroupPrimitive(PrimitiveRenderEvent pre, boolean drawText){
		if ( _iun == null )
		{
			logger.log( ILogger.WARNING,
					Messages.getString( "exception.missing.component.interaction", getLocale( ) ) );