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
protected void setCursor( Element currentElement )
	{
		String style = currentElement.getAttribute( "style" ); 
		if ( style == null )
		{
			style = ""; 
		}
		currentElement.setAttribute( "style", style + "cursor:pointer;" ); 
	}
		
	/**
	 * 
	 * @param iArcStyle
	 * @return
	 */
	private static final int toSwingArcType( int iArcStyle )
	{
		switch ( iArcStyle )
		{
			case ArcRenderEvent.OPEN :
				return Arc2D.OPEN;
			case ArcRenderEvent.CLOSED :
				return Arc2D.CHORD;
			case ArcRenderEvent.SECTOR :
				return Arc2D.PIE;
		}
		return -1;
	}
	/**
	 * Locates a design-time series corresponding to a given cloned run-time