Bug 139346 Using isTopN in table inside list group header doesn't work.
Description: Using isTopN in table inside list group header doesn't work. Steps to reproduce: 1.Insert a list with a group 2.Insert a table to list group header 3.Using Total.isTopN(row[],2,null,0) as filter expression in table item. 4.Preview Result: Only the first group displayed top 2 records, other groups kept display all records.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/QueryExecutor.java
/**
	 * Executes the ODI query to reproduce a ODI result set
	 * @param eventHandler 
	 * 
	 * @return
	 */
	abstract protected IResultIterator executeOdiQuery(
			IEventHandler eventHandler ) throws DataException;
		
	/**
	 * @param context
	 */
	void setAppContext( Map context )
	{
	    queryAppContext = context;
	}
	
	/**
	 * Prepare Executor so that it is ready to execute the query
	 * 
	 * @param outerRts
	 * @param targetScope
	 * @throws DataException
	 */
	void prepareExecution( IQueryResults outerRts, Scriptable targetScope ) throws DataException
	{
		if(isPrepared)return;
		
		this.parentScope = targetScope;