Bug 123523 Previewing a scripted data set mapped to a java event handler throws NPE
When previewing a scripted data set we try to get a class loader from the ExecutionContext. (See ScriptExecutor.getClassUsingCustomClassPath). The context will be null in this case. The reason for using the context is to use cached class loaders when possible. Need to use some other mechanism to get the class loader if the context is null. We can either provide an external map to use as cache, or not bother with caching at all.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/script/internal/instance/ReportElementInstance.java
{
	protected AbstractContent content;
	private ExecutionContext context;
	public ReportElementInstance( AbstractContent content,
			ExecutionContext context )
	{
		this.content = content;
		this.context = context;
	}
	protected ReportElementInstance( ExecutionContext context )
	{
		this.context = context;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.engine.api.script.instance.IReportInstance#getStyle()
	 */
	public IScriptStyle getStyle( )
	{
		return new StyleInstance( content.getStyle( ) );
	}
	public Object getNamedExpressionValue( String name )
	{
		Object generatedBy = content.getGenerateBy( );