Bug 15477: (follow-up) Bug 14100: Better errors handling

Bug 15477: (follow-up) Bug 14100: Better errors handling

On bug 14100, the patch "Better errors handling" introduced an ...
error.
The user always get "An error occurred when updating this translation"
although it has been updated in DB.

Test plan:
Edit translations for an item type: you should not get an error when
everything went fine.

Tested on top of 15487, error message does no longer appear.
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Brendan Gallagher brendan@bywatersolutions.com
(cherry picked from commit e706cd18f0d24365a197ac50fe77d7dc16014ca6)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>