GetNextLayoutLeaf() returns the next container, not the follow one, so
calls to that without checking first if we are in a table are always
suspicious. This leads at the end to strange content move, as described
in the bug.

There appears to be only a single place in SwFrame::GetNextSctLeaf()
which may be executed for split sections and called GetNextLayoutLeaf()
unconditionally.

Change-Id: I759d9ef63660f3d2ffe006c88b18cba7dba99f33
Reviewed-on: https://gerrit.libreoffice.org/41882Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>