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/parser/EngineIRVisitor.java
{
		
		CellDesign cell = new CellDesign( );
		setupStyledElement( cell, handle );
		
		SlotHandle contentSlot = handle.getContent( );
		for ( int i = 0; i < contentSlot.getCount( ); i++ )
		{
			apply( contentSlot.get( i ) );
			if ( currentElement != null )
			{
				cell.addContent( (ReportItemDesign) currentElement );
			}
		}
		
		
		
		cell.setColSpan( handle.getColumnSpan( ) );
		int columnId = handle.getColumn( ) - 1;
		if ( columnId < 0 )
		{
			columnId = -1;
		}
		cell.setColumn( columnId );
		
		cell.setRowSpan( handle.getRowSpan( ) );
		cell.setDrop( handle.getDrop( ) );
		currentElement = cell;
	}
	/**