 			try
 			{
 				this.xlsSheetsArray = xlsSheetsArray;
-				if (_attributeHierarchy.value == null)
+				if (_attributeHierarchy.value == null && xlsSheetsArray.length > 0)
 				{
 					// loop through column names, adding indicators to hierarchy
 					var firstRow:Array = xlsSheetsArray[0].values[0];

		{
		}
		
		override protected function initialize():void
		{
			super.initialize();

			var colName:String = String(proxyColumn.getMetadata("name"));
			var colIndex:int = getColumnIndexFromSheetValues(xlsSheetsArray[0].values[0],colName);
			var keyColIndex:int = getColumnIndexFromSheetValues(xlsSheetsArray[0].values[0],keyColName.value);

			var xlsDataColumn:Vector.<String> = getColumnValues(colIndex);
			var keyStringsArray:Array = VectorUtils.copy(getColumnValues(keyColIndex), []);
