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
package org.eclipse.birt.data.engine.script;
import org.eclipse.birt.core.data.DataTypeUtil;
import org.eclipse.birt.core.exception.BirtException;
import org.eclipse.birt.data.engine.api.IConditionalExpression;
import org.eclipse.birt.data.engine.api.IScriptExpression;
import org.eclipse.birt.data.engine.cache.BasicCachedArray;
import org.eclipse.birt.data.engine.core.DataException;
import org.eclipse.birt.data.engine.expression.ExprEvaluateUtil;
import org.eclipse.birt.data.engine.i18n.ResourceConstants;
import org.eclipse.birt.data.engine.impl.IExecutorHelper;
import org.mozilla.javascript.Context;
import org.mozilla.javascript.Scriptable;
/**
 * The implementation of this class is used to evaluate TopN/BottomN expressions 
 * @author lzhu
 *
 */
public abstract class NEvaluator