Bug 135778 There is an error when the data item has no binding data set
Data item can have no binding data set, if it happens, it indicates it only use the basic Java Script function such as new Date(). At this moment, the data of data item is not stored in report document by DtE, which only supports these data items which has binding data set.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/PreparedDataSourceQuery.java
public IQueryResults execute( IQueryResults outerResults, Scriptable scope )
			throws DataException
	{
		return preparedQuery.doPrepare( outerResults,
				scope,
				newExecutor( ),
				this );
	}
	
	/**
	 * @return the appropriate subclass of the Executor
	 */
	protected abstract QueryExecutor newExecutor( );
	
	/*
	 * @see org.eclipse.birt.data.engine.impl.IPreparedQueryService#execSubquery(org.eclipse.birt.data.engine.odi.IResultIterator,
	 *      java.lang.String, org.mozilla.javascript.Scriptable)
	 */
	public QueryResults execSubquery( IResultIterator iterator,
			String subQueryName, Scriptable subScope ) throws DataException
	{
		return this.preparedQuery.execSubquery( iterator,
				subQueryName,
				subScope );
	}
	
	/**
	 * 
	 */
	abstract class DSQueryExecutor extends QueryExecutor