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
import org.eclipse.birt.chart.model.attribute.ActionType;
import org.eclipse.birt.chart.model.attribute.Bounds;
import org.eclipse.birt.chart.model.attribute.EmbeddedImage;
import org.eclipse.birt.chart.model.attribute.Location;
import org.eclipse.birt.chart.model.attribute.Position;
import org.eclipse.birt.chart.model.attribute.ScriptValue;
import org.eclipse.birt.chart.model.attribute.TooltipValue;
import org.eclipse.birt.chart.model.attribute.TriggerCondition;
import org.eclipse.birt.chart.model.attribute.URLValue;
import org.eclipse.birt.chart.model.component.Axis;
import org.eclipse.birt.chart.model.component.Series;
import org.eclipse.birt.chart.model.data.SeriesDefinition;
import org.eclipse.birt.chart.model.data.Trigger;
import org.eclipse.birt.chart.model.layout.LabelBlock;
import org.eclipse.birt.chart.model.layout.Legend;
import org.eclipse.birt.chart.model.layout.Plot;
import org.eclipse.birt.chart.model.layout.TitleBlock;
import org.eclipse.birt.chart.util.Base64;
import org.eclipse.birt.chart.util.PluginSettings;
import org.eclipse.emf.common.util.EList;
import org.w3c.dom.DOMImplementation;
import org.w3c.dom.Document;
import org.w3c.dom.DocumentType;
import org.w3c.dom.Element;
/**
 * Provides a reference implementation of a SVG device renderer. It translates
 * chart primitives into standard SVG v1.1 rendering primitives.
 */
public class SVGRendererImpl extends SwingRendererImpl
{