[BUGFIX] Fix minor phpstan finding in ElementInformationController

This fixes a possible call to the getReadablePath method on
InaccessibleFolder by checking, whether the instance is of type Folder.

Resolves: #100991
Releases: main, 12.4
Change-Id: I8161168c9d8facb314253cba5893e4296e76282b
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/79250


Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>