[BUGFIX] Add use-statement for GeneralUtility

With Change-Id: I57a2a2a06a97fc1eda6e0438bfdc6e210437e5bb
a line was packported which relied on a use-statement
for GeneralUtility. Since GeneralUtility is often used
in this class, simply add a use-statement.

Change-Id: Ifc8efbf97427a84e160c3e406b6a3e1dc1b7df1d
Resolves: #60595
Releases: 6.1
Reviewed-on: http://review.typo3.org/31843
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>