Error thrown when trying to write spreadsheet "Undefined array key in Calculation"

[allredbm]

I have a simple program that opens a spreadsheet, adds a test phrase to cell A6, and writes the result to a new file:

`use PhpOffice\PhpSpreadsheet\Reader\Xlsx as Reader;
use PhpOffice\PhpSpreadsheet\Spreadsheet;
use PhpOffice\PhpSpreadsheet\Writer\Xlsx as Writer;

$docLocation = "[file location]";

$reader = new Reader();
$spreadsheet = $reader->load($docLocation);
// $sheet = $spreadsheet->getSheet(0);
// $sheet->setCellValue('A6', 'Test');

$writer = new Writer($spreadsheet);
$fileName = "[new file location]";
$writer->save($fileName);
var_dump($fileName);`

I've confirmed that most of the program works just fine, but when it reaches "$writer->save($fileName)" it throws this error:

PHP Warning: Undefined array key "" in C:\inetpub\wwwroot\vendor\phpoffice\phpspreadsheet\src\PhpSpreadsheet\Calculation\Calculation.php on line 4367 PHP Fatal error: Uncaught TypeError: array_keys(): Argument #1 ($array) must be of type array, null given in C:\inetpub\wwwroot\vendor\phpoffice\phpspreadsheet\src\PhpSpreadsheet\Calculation\Calculation.php:4367 Stack trace: #0 C:\inetpub\wwwroot\vendor\phpoffice\phpspreadsheet\src\PhpSpreadsheet\Calculation\Calculation.php(4367): array_keys(NULL) #1 C:\inetpub\wwwroot\vendor\phpoffice\phpspreadsheet\src\PhpSpreadsheet\Calculation\Calculation.php(4487): PhpOffice\PhpSpreadsheet\Calculation\Calculation::dataTestReference(Array) #2 C:\inetpub\wwwroot\vendor\phpoffice\phpspreadsheet\src\PhpSpreadsheet\Calculation\Calculation.php(3539): PhpOffice\PhpSpreadsheet\Calculation\Calculation->processTokenStack(Array, 'B2', Object(PhpOffice\PhpSpreadsheet\Cell\Cell)) #3 C:\inetpub\wwwroot\vendor\phpoffice\phpspreadsheet\src\PhpSpreadsheet\Calculation\Calculation.php(3332): PhpOffice\PhpSpreadsheet\Calculation\Calculation->_calculateFormulaValue('IFERROR(IF(INDI...', 'B2', Object(PhpOffice\PhpSpreadsheet\Cell\Cell)) #4 C:\inetpub\wwwroot\vendor\phpoffice\phpspreadsheet\src\PhpSpreadsheet\Cell\Cell.php(259): PhpOffice\PhpSpreadsheet\Calculation\Calculation->calculateCellValue(Object(PhpOffice\PhpSpreadsheet\Cell\Cell), true) #5 C:\inetpub\wwwroot\vendor\phpoffice\phpspreadsheet\src\PhpSpreadsheet\Writer\Xlsx\Worksheet.php(1229): PhpOffice\PhpSpreadsheet\Cell\Cell->getCalculatedValue() #6 C:\inetpub\wwwroot\vendor\phpoffice\phpspreadsheet\src\PhpSpreadsheet\Writer\Xlsx\Worksheet.php(1300): PhpOffice\PhpSpreadsheet\Writer\Xlsx\Worksheet->writeCellFormula(Object(PhpOffice\PhpSpreadsheet\Shared\XMLWriter), '=IFERROR(IF(IND...', Object(PhpOffice\PhpSpreadsheet\Cell\Cell)) #7 C:\inetpub\wwwroot\vendor\phpoffice\phpspreadsheet\src\PhpSpreadsheet\Writer\Xlsx\Worksheet.php(1156): PhpOffice\PhpSpreadsheet\Writer\Xlsx\Worksheet->writeCell(Object(PhpOffice\PhpSpreadsheet\Shared\XMLWriter), Object(PhpOffice\PhpSpreadsheet\Worksheet\Worksheet), 'B2', Array) #8 C:\inetpub\wwwroot\vendor\phpoffice\phpspreadsheet\src\PhpSpreadsheet\Writer\Xlsx\Worksheet.php(70): PhpOffice\PhpSpreadsheet\Writer\Xlsx\Worksheet->writeSheetData(Object(PhpOffice\PhpSpreadsheet\Shared\XMLWriter), Object(PhpOffice\PhpSpreadsheet\Worksheet\Worksheet), Array) #9 C:\inetpub\wwwroot\vendor\phpoffice\phpspreadsheet\src\PhpSpreadsheet\Writer\Xlsx.php(377): PhpOffice\PhpSpreadsheet\Writer\Xlsx\Worksheet->writeWorksheet(Object(PhpOffice\PhpSpreadsheet\Worksheet\Worksheet), Array, false) #10 C:\inetpub\wwwroot\App\Services\export-excel-cg.php(57): PhpOffice\PhpSpreadsheet\Writer\Xlsx->save('../../Public/Fi...') #11 {main} thrown in C:\inetpub\wwwroot\vendor\phpoffice\phpspreadsheet\src\PhpSpreadsheet\Calculation\Calculation.php on line 4367

I've tried running this program with a blank excel document and I didn't get any errors when I did. I don't think there's anything in the excel file I'm testing with that should trip it up, but I'm not totally sure based on the documentation. Has anyone else run into this?