[BUGFIX] Improve FalUpdateWizard

Add an additional check to get the correct file

Resolves: #61610
Change-Id: I00fca22ba53ad1f92459dd0f8c5587848a7d6b8f
Reviewed-on: http://review.typo3.org/33281
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>