Fix exact MATCH on ranges with empty cells (#1520)
Fixes a bug when doing exact match on ranges with empty cells.
```php
<?php
require 'vendor/autoload.php';
use PhpOffice\PhpSpreadsheet\Spreadsheet;
$spreadsheet = new Spreadsheet();
$sheet = $spreadsheet->getActiveSheet();
// Row: 1, null, 4, null, 8.
$sheet->getCell('A1')->setValue(1);
$sheet->getCell('A3')->setValue(4);
$sheet->getCell('A5')->setValue(8);
$sheet->getCell('B1')->setValue('=MATCH(4, A1:A5, 1)');
// Should echo 3, but echos '#N/A'.
echo $sheet->getCell('B1')->getCalculatedValue() . PHP_EOL;
// Row: 1, null, 4, null, null.
$sheet->getCell('C1')->setValue(1);
$sheet->getCell('C3')->setValue(4);
$sheet->getCell('D1')->setValue('=MATCH(5, C1:C5, 1)');
// Should echo 3, but echos '#N/A'.
echo $sheet->getCell('D1')->getCalculatedValue() . PHP_EOL;
```
73c336ac96