Header columns can disappear with filtered data in pivot tables

Header columns can disappear with filtered data in pivot tables

When we set on a pivot table a filter that filters all the rows,
the pivot table showed only the first header columns and computed
column, but all the columns headers should still be shown so we can
adjust the filter for the column. This fixes this issue.

Also add more debug output and prevent a crash when running pivot
table tests.

Change-Id: I30b4ee72cf8436c4522ab4ba0781462b214816dd
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/151871
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
(cherry picked from commit 3551d18404cb19cdaa8edb170a549f5c5405d0cb)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/153686
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
(cherry picked from commit 3a51b402f243eb32b544c16813f682617d88c0b9)