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
* @return content count
	 */
	public int getContentCount( )
	{
		return this.contents.size( );
	}
	/**
	 * get content at index.
	 * 
	 * @param index
	 *            content index
	 * @return content
	 */
	public ReportItemDesign getContent( int index )
	{
		assert ( index >= 0 && index < this.contents.size( ) );
		return (ReportItemDesign) this.contents.get( index );
	}
	/**
	 * add content in to report body.
	 * 
	 * @param item
	 *            content to be added.
	 */
	public void addContent( ReportItemDesign item )
	{
		this.contents.add( item );
	}
	/**
	 * get number of shared styles defined in this report.