Since ScTokenArray::Add() overallocates memory, make sure we do not
keep such possibly large arrays. Since any copying of ScTokenArray
implicitly finalizes as well, this is not a big problem right now,
but then why needlessly do the copies? (next commit)

Change-Id: I55398bcd8fb31f1be5a4b8e3f5a71b26649a7594
Reviewed-on: https://gerrit.libreoffice.org/60862
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>