[TASK] Sanitize idn_to_ascii with empty string

idn_to_ascii() must not be called with empty
string in PHP 8.4.

Resolves: #104587
Related: #104513
Releases: main, 12.4, 11.5
Change-Id: I649d157cca3dadbe237e20eb440b071a1885db71
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/85581


Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Jasmina Ließmann <minapokhalo+typo3@gmail.com>
Tested-by: Jasmina Ließmann <minapokhalo+typo3@gmail.com>
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/85583