The problem with the bugdoc is that SwFrame::GetNextSctLeaf() creates a
follow frame for a section in a table, and puts it outside the table,
below the page's body frame, while moving text frames that have the
mbInfTab flag set into the follow frame.

The situation is different from forcepoint #18 though: the frame "this"
is a SwTabFrame here, and GetNextCellLeaf() *does* return a plausible
looking follow cell frame, however it's ignored later because
CanContainSplitSection(this) is false since it's a SwTabFrame.

IIRC table-in-section-in-table should not be split anyway, so
just add a check here and return early.

(regression f8a76d21)

Revert "forcepoint #3"
This reverts commit 34627ad7
because it was just a work-around not to crash with the invalid table
frames.

Change-Id: I54692a67edade23c6b8e0a9be806728b0012a3fd
Reviewed-on: https://gerrit.libreoffice.org/51751Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
(cherry picked from commit 5e18136a)
Reviewed-on: https://gerrit.libreoffice.org/52383
(cherry picked from commit 20e1544a)