php8.0 버전 호환 코드 적용 및 PHP 끝 태그 삭제 일괄적용

lib/PHPExcel/Shared/ZipStreamWrapper.php

@@ -76,7 +76,7 @@ class PHPExcel_Shared_ZipStreamWrapper
     public function stream_open($path, $mode, $options, &$opened_path)
     {
         // Check for mode
-        if ($mode{0} != 'r') {
+        if ($mode[0] != 'r') {
             throw new PHPExcel_Reader_Exception('Mode ' . $mode . ' is not supported. Only read mode is supported.');
         }