[BUGFIX] Mount point initialization stops on invalid mountpoint

Continue with next mountpoint.

Change-Id: I51288cb4e806a64f69946c6c1c695defa619e65a
Resolves: #54538
Reviewed-on: https://review.typo3.org/26577
Reviewed-by: Stefan Neufeind
Reviewed-by: Hans Höchtl
Tested-by: Hans Höchtl