[BUGFIX] Fix PHP 8 warning in ConstantConfigurationParser

If extension authors don't provide a type for their
extension configuration options, they will now fall
back to "string" and prevent later undefined array
key access warnings.

Resolves: #95977
Releases: master
Change-Id: Icd77c4d130d2fc7d0b4f127dbeb2926c4057b81c
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72175
Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>

typo3/sysext/core/Classes/TypoScript/Parser/ConstantConfigurationParser.php

@@ -296,6 +296,8 @@ public function parseComments($flatSetup, $default = null): array
                 $editableComments[$const]['name'] = $const;
                 $editableComments[$const]['value'] = trim($value);
                 $editableComments[$const]['default_value'] = trim((string)($default[$const] ?? ''));
+                // If type was not provided, initialize with default value "string".
+                $editableComments[$const]['type'] ??= 'string';
             }
         }
         return $editableComments;