In preparation of forward-porting the distro/collabora/cp-6.0-only
commit 418adc09 (lo: disable under-used
hyperlink fields that are buggy online., 2019-05-22), which relaxes the
invariant that mpLbForm never returns LISTBOX_ENTRY_NOTFOUND.

A signed integer overflow is a problem in itself, but in practice the
SID_HYPERLINK_SETLINK handler in sd::DrawViewShell::FuTemporary() didn't
insert a field, since the insert mode was a large negative value instead
of HLINK_FIELD.

[ master -> cp-6.0 backport note: on this branch, this fixes a
regression. ]

Conflicts:
	cui/source/dialogs/hltpbase.cxx

Change-Id: I238d9f662a74f320d05ea6a6cc97319d2d5b3d5a
Reviewed-on: https://gerrit.libreoffice.org/73036Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
Tested-by: Michael Meeks <michael.meeks@collabora.com>