Bug 136027 [Smoke]the report with a gounp can not preview
Description: the report with a gounp can not preview Steps to reproduce: 1. new a datasource and a dataset 2. drag the dataset to the layout 3. Add a group on the table. save and preview. Actual result: "Error happened while running the report" is appeared.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/GroupDialog.java
{
					inputGroup.setTocExpression( newToc );
				}
			}
			int index = keyChooser.getSelectionIndex( );
			String oldKeyExpr = inputGroup.getKeyExpr( );
			String newKeyExpr = keyChooser.getText( );
			inputGroup.setKeyExpr( newKeyExpr );
			if ( newKeyExpr != null
					&& newKeyExpr.length( ) != 0
					&& !newKeyExpr.equals( oldKeyExpr ) )
			{
				SlotHandle slotHandle = null;
				
				if ( inputGroup instanceof ListGroupHandle )
				{
					slotHandle = inputGroup.getHeader( );
					
					
				}
				else if ( inputGroup instanceof TableGroupHandle )
				{
					if ( inputGroup.getHeader( ).getCount( ) != 0 )
					{
						RowHandle rowHandle = ( (RowHandle) inputGroup.getHeader( )
								.get( 0 ) );
						CellHandle cellHandle = (CellHandle) rowHandle.getCells( )
								.get( 0 );
						slotHandle = cellHandle.getContent( );
					}