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
protected PageSetupDesign pageSetup = new PageSetupDesign( );
	/**
	 * Report body
	 */
	protected ArrayList contents = new ArrayList( );
	protected Map namedExpressions;
	
	/**
	 * The base directory of the relative links. By default it is where design
	 * file (XML) resides
	 */
	protected String basePath;
	/**
	 * The prefix of style name
	 */
	public static final String PREFIX_STYLE_NAME = "style_"; 
	/**
	 * default constructor.
	 */
	public Report( )
	{
	}
	public Map getNamedExpressions( )
	{
		if( namedExpressions == null )
			namedExpressions = new HashMap( );
		
		return namedExpressions;
	}
	/**