Bug 201017 TopN, TopPercent, BottomPercent filters will lead NPE when the values contains NULL[07]
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/script/NEvaluator.java
{
	private BasicCachedArray valueList; 
	private BasicCachedArray rowIdList;
	private int firstPassRowNumberCounter = 0;
	private int secondPassRowNumberCounter = 0;
	private int qualifiedRowCounter = 0;
	
	
	private int N = -1;
	
	
	private boolean n_percent = false;
	
	
	private IScriptExpression op_expr;
	 
	private IScriptExpression n_expr;
	
	private FilterPassController filterPassController;