[BUGFIX] Only return translation count message for a non-zero count

With #93979, `BackendUtility::translationCount()` was changed and always
returned the message "This record has X translation(s) [...]!" even if
there are no translated records at all.

This patch initializes `$count` as 0 and changes the message handling as
similar as in `BackendUtility::referenceCount()`.

Resolves: #94091
Related: #93979
Releases: master
Change-Id: I43dfa860d1c278a239bd88e83feddf239b8b01a8
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/69066


Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Benjamin Franzke <bfr@qbus.de>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Benjamin Franzke <bfr@qbus.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>