[BUGFIX] Allow setting translateToMessage to empty

Unsetting TCEMAIN.translateToMessage was not possible
due to a default fallback to a hardcoded string in
data handler.

This patch sets the default via PageTSConfig and
simplifies the condition / fallback logic.

Change-Id: Ie06410126a83de0e158c43cbfd6ee3d45176c363
Resolves: #82523
Releases: master
Reviewed-on: https://review.typo3.org/54429


Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>