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
Messages.getString( "info.toggle.visibility", 
										getLocale() )
										+ seRT );
						Series seDT = null;
						try
						{
							
							
							
														
							seDT = findDesignTimeSeries( seRT ); 
							List components = (List)componentPrimitives.get(seDT);
							if (components != null){
								Iterator iter = components.iterator();
								StringBuffer sb = new StringBuffer();
								sb.append(seDT.hashCode());
								if (iter.hasNext())
									sb.append(",new Array(");							 
								while (iter.hasNext()){
									sb.append("'").append(iter.next()).append("'"); 
									if (iter.hasNext())
										sb.append(","); 
								}
								if (components.size() > 0)
									sb.append(")"); 
								elm.setAttribute("onmousedown", 
										"toggleVisibility(evt, " 
												+ sb.toString() + ")"); 							
								setCursor(elm);