From 4c4ae2634f7774f7e4763c38cf00a7afebb02323 Mon Sep 17 00:00:00 2001
From: Roland Eigelsreiter <brainfoolong@users.noreply.github.com>
Date: Mon, 1 Nov 2021 03:45:21 +0100
Subject: [PATCH] fixed null conversation for strToUpper (#2292)

fixed in the same way as it already has been done for strToLower

Co-authored-by: Adrien Crivelli <adrien.crivelli@gmail.com>
---
 src/PhpSpreadsheet/Shared/StringHelper.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/PhpSpreadsheet/Shared/StringHelper.php b/src/PhpSpreadsheet/Shared/StringHelper.php
index d1422c76..435d0e4c 100644
--- a/src/PhpSpreadsheet/Shared/StringHelper.php
+++ b/src/PhpSpreadsheet/Shared/StringHelper.php
@@ -490,7 +490,7 @@ class StringHelper
      */
     public static function strToUpper($textValue)
     {
-        return mb_convert_case($textValue, MB_CASE_UPPER, 'UTF-8');
+        return mb_convert_case($textValue ?? '', MB_CASE_UPPER, 'UTF-8');
     }
 
     /**