Bug 8399: Display tab number on the mandatory field alert (authority)

Bug 8399: Display tab number on the mandatory field alert (authority)

A wrong variable scope was used here, the number value is contained in
the BIG_LOOP (note for later: change this variable name...).

Test plan:
1/ Define 1+ mandatory fields for an authority type
2/ Create an authority and don't fill the mandatory fields
3/ Try to save: the popup alert should display the number of the tab.

Signed-off-by: Andreas Hedström Mace <andreas.hedstrom.mace@sub.su.se>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>