tdf#114536 sw: fix use-after-free in SwTextFormatter::MergeCharacterBorder()

SwTextFormatter::Underflow() truncated a line portion, which deletes the
rest of the line portions, but left m_pFirstOfBorderMerge unchanged,
leading to a crash when SwTextFormatter::MergeCharacterBorder() tried to
access it.

Fix the problem by updating the non-owning m_pFirstOfBorderMerge
accordingly when truncating the line portion.

Change-Id: I5e445bbe2424d70d60c363fa4e3a00636e282325
Reviewed-on: https://gerrit.libreoffice.org/47923
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>

0 files changed, 0 insertions, 0 deletions