[BUGFIX] Avoid remapping empty value in checkValueForInline

This change prevents checkValueForInline from processing
empty values. The existing check would process empty
values since one of the true matches is when value cannot
be interpreted as an integer.

Change-Id: Iacd38363bcc23453da9fcc2eea359680c6b91175
Resolves: #79063
Releases: master, 7.6
Reviewed-on: https://review.typo3.org/51015


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Thomas Hohn <thomas@hohn.dk>
Tested-by: Thomas Hohn <thomas@hohn.dk>
Reviewed-by: Christer V <cvi@systime.dk>
Reviewed-by: Kasper Ligaard <kasperligaard+typo3.org@gmail.com>
Reviewed-by: Markus Sommer <markussom@posteo.de>
Tested-by: Markus Sommer <markussom@posteo.de>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Oliver Hader <oliver.hader@typo3.org>