Bug 21279: Fix   in transport cost matrix

Bug 21279: Fix   in transport cost matrix

Test plan:
On Home › Administration › Transport cost matrix you should no longer
see " ".
Fill some values and save, you should see the correct values.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(cherry picked from commit 1fddd295b8e83b60f2b838f09f3175c5acfeec28)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>