justify range to prevent negative tab span and memory alloc, rhbz#1057741

I could not reproduce the crash of that bug (probably having more memory
available), but the backtrace had nTabSpan = -2 implicitly casted to
size_t leading to allocation of a huge amount of memory with
vector::reserve(), which ScRange::Justify() exactly prevents.

Change-Id: Idb79e1be62649922ba793cab01e00011479fade9
(cherry picked from commit a45fde7235f95792bf8e6f6979d0040637c5785d)
Reviewed-on: https://gerrit.libreoffice.org/8624
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>