Bug 23823: (follow-up) Get rid of some tabs in favor of spaces

Bug 23823: (follow-up) Get rid of some tabs in favor of spaces

In the paragraph touched by this patch, there were some
whitespace issues. This patch does some tab to space
replacement and reindentation to make the code more readable.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Ivan Masár <helix84@centrum.sk>
Signed-off-by: Séverine QUEUNE <severine.queune@bulac.fr>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>