[BUGFIX] Fresh tag in TypoScriptConstantsViewHelper per call

With current fluid, the TypoScriptConstantsViewHelper is
instantiated only once and re-used if called multiple times.
$this->tag is then polluted from previous runs and creates
funny results.
Fix by re-initializing that property each call.

Resolves: #83319
Releases: master
Change-Id: Idf9e14ca69e76278bd0d6eaca1fec9b93c238fd5
Reviewed-on: https://review.typo3.org/55273


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Henning Liebe <h.liebe@neusta.de>
Reviewed-by: Jan Stockfisch <jan.stockfisch@googlemail.com>
Reviewed-by: Reiner Teubner <reiner.teubner@me.com>
Tested-by: Reiner Teubner <reiner.teubner@me.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>