freezePane leaving incorrect cell selected

[ant-g]

This is:

- [x] a bug report
- [ ] a feature request
- [ ] **not** a usage question (ask them on https://stackoverflow.com/questions/tagged/phpspreadsheet or https://gitter.im/PHPOffice/PhpSpreadsheet)

What is the expected behavior?

When calling freezePane the cell is frozen above and to left of selected cell and selected cell is 'selected'

What is the current behavior?

When calling freezePane the cell is frozen above and to left of selected cell and the cell 1 row below the selected cell is 'selected'

What are the steps to reproduce?

require __DIR__ . '/vendor/autoload.php';
use PhpOffice\PhpSpreadsheet\Spreadsheet;
use PhpOffice\PhpSpreadsheet\IOFactory;

$spreadsheet = new Spreadsheet();
// Add some data
$spreadsheet->setActiveSheetIndex(0)
    ->setCellValue('A1', 'Hello')
    ->setCellValue('A2', 'world!')
    ->setCellValue('A3', 'Hello')
    ->setCellValue('A4', 'world!');	
	
$spreadsheet->getActiveSheet()->freezePane('A2');

// Redirect output to a client’s web browser (Xlsx)
header('Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
header('Content-Disposition: attachment;filename="01simple.xlsx"');
header('Cache-Control: max-age=0');
// If you're serving to IE 9, then the following may be needed
header('Cache-Control: max-age=1');
// If you're serving to IE over SSL, then the following may be needed
header('Expires: Mon, 26 Jul 1997 05:00:00 GMT'); // Date in the past
header('Last-Modified: ' . gmdate('D, d M Y H:i:s') . ' GMT'); // always modified
header('Cache-Control: cache, must-revalidate'); // HTTP/1.1
header('Pragma: public'); // HTTP/1.0
	
$writer = IOFactory::createWriter($spreadsheet, 'Xlsx');
$writer->save('php://output');
exit;

can be corrected by explicitly providing 'topLeftCell' argument

$spreadsheet->getActiveSheet()->freezePane('A2','A2');

but seems to me that the code at line 1991 in worksheet.php should change from

 $topLeftCell = $coordinate[0] . ($coordinate[1]+1);

to

  $topLeftCell = $coordinate[0] . $coordinate[1];

?

Which versions of PhpSpreadsheet and PHP are affected?

PhpSpreadsheet Based on current non-dev composer deployment. V1.1
PHP v7.0