Bug 121687 Exception throws when export data in table which inside a grid cell.
Description: Exception throws when export data in table which inside a grid cell. Steps to reproduce: 1. insert a grid. 2. insert one table to one grid cell. 3. insert another table to the other grid cell. 4. export data in two tables. Expected result: Data are exported. Actual result: Exception in: ReportEngineService.getMetaData( )
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/ir/Report.java
/**
	 * default unit
	 */
	protected String unit;
	/**
	 * styles used in this report
	 */
	protected ArrayList styles = new ArrayList( );
	/**
	 * style-name mapping table
	 */
	protected HashMap styleTable = new HashMap( );
	/**
	 * A collection that stores the top level report parameters and parameter
	 * groups.
	 */
	protected ArrayList parameters = new ArrayList( );
	/**
	 * queries used by this report.
	 * 
	 * @see org.eclipse.birt.report.engine.anlyzer.IQueryDefinition
	 */
	protected ArrayList queries = new ArrayList( );
	/**
	 * use to find the query IDs.(query, string) pair.
	 */
	protected HashMap queryIDs = new HashMap( );
	/**
	 * Page setup this report used
	 */