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
}
	private void setKeyExpression( String key )
	{
		keyChooser.deselectAll( );
		if ( StringUtil.isBlank( key ) )
		{
			keyChooser.setText( "" ); 
			return;
		}		
		keyChooser.setText( key );
	}
	/**
	 * Reset interval
	 * 
	 */
	private void resetInterval( )
	{
		String currentKeyExpression = keyChooser.getText( );
		if ( previoiusKeyExpression.equals( currentKeyExpression ) )
			return;
		if ( ExpressionUtility.isColumnExpression( currentKeyExpression ) )
			intervalChoices = getSubIntervalChoice( );
		else
			intervalChoices = intervalChoicesAll;
		resetIntervalType( intervalChoices );
		previoiusKeyExpression = currentKeyExpression;
	}
	/**
	 * Get subIntervalChoice, could be String,Date,Numeric or All
	 *