fix 5.4 regression from 4605bd46.

When there are columns, if a nextpage section doesn't contain any
other "page style" details we treat it as a continuous break,
If we don't, the column info becomes part of the style itself,
and not just a section property.

However, the very first section is troublesome - by definition it DOES
contain page style details, and so if the document starts with columns,
the default style would gain the column attribute. Usually that
results in a mess, so lets make sure that we avoid that also in
the case where headers/footers are defined.

Change-Id: I7e08a9218e4304206579ed064bc92c9604d4470e
Reviewed-on: https://gerrit.libreoffice.org/44505Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Justin Luth <justin_luth@sil.org>
Tested-by: Justin Luth <justin_luth@sil.org>