Bug 201030 NPE throws out when preview the attached report design
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/script/ScriptEvalUtil.java
* @param expr
	 * @param cx
	 * @param scope
	 * @param source
	 * @param lineNo
	 * @return 
	 * @throws DataException
	 */
	public static Object evalExpr( IBaseExpression expr, Context cx, Scriptable scope, 
				String source, int lineNo )
		throws DataException
	{
		if ( logger.isLoggable( Level.FINER ) )
			logger.entering( ScriptEvalUtil.class.getName( ),
				"evalExpr",
				"evalExpr() expr="
						+ LogUtil.toString( expr ) + ", source=" + source
						+ ", lineNo=" + lineNo );
		Object result;
		if ( expr == null )
		{
			result = null;
		}
		else if ( expr instanceof IConditionalExpression )
		{
			
			Object handle = expr.getHandle( );
			if ( handle instanceof NEvaluator )
			{
				result = Boolean.valueOf( ( (NEvaluator) handle ).evaluate( cx,