Fix isEmptyRow() check

src/Spout/Reader/XLSX/RowIterator.php

@@ -340,7 +340,7 @@ class RowIterator implements IteratorInterface
      */
     protected function isEmptyRow($rowData)
     {
-        return (count($rowData) === 1 && key($rowData) === '');
+        return (count($rowData) === 1 && reset($rowData) === '');
     }
 
     /**