compatibility advice: must be of the type string, null given

[FFCZ]

question: when i load xlsx，a little error occurred

File : E:\htdocs\vendor\phpoffice\phpspreadsheet\src\PhpSpreadsheet\Shared\StringHelper.php
Error : Argument 1 passed to PhpOffice\PhpSpreadsheet\Shared\StringHelper::strToLower() must be of the type string, null given,
Call : called in E:\htdocs\vendor\phpoffice\phpspreadsheet\src\PhpSpreadsheet\Calculation\LookupRef\VLookup.php on line 71

original code
public static function strToLower(string $textValue): string { return mb_convert_case($textValue, MB_CASE_LOWER, 'UTF-8'); }
suggest improvements, support null, php >=7.1
public static function strToLower(?string $textValue): string { return mb_convert_case($textValue, MB_CASE_LOWER, 'UTF-8'); }
thank you !

[MarkBaker]

Depending on the version of PhpSPreadsheet that you're running, this is fixed in VLookup.php where the value passed to StringHelper::strToLower() is explicitly cast to a string:

        $aLower = StringHelper::strToLower((string) $a[$firstColumn]);
        $bLower = StringHelper::strToLower((string) $b[$firstColumn]);

Duplicate of Issue #2934 resolved by PR #2939 (commit 4bf4278) and release in version 1.24.1