Revised the fix to make it also work with the dummy data format.

Signed-off-by: Daniel Scheffler <danschef@gfz-potsdam.de>
3 jobs for 79-filenotfounderror-when-using-the-official-enmap-test-data-downloaded-from-enmap-org in 17 minutes and 39 seconds (queued for 2 seconds)