fdo#45447: add an assertion when anchored to page 0
fdo#45447: add an assertion when anchored to page 0

XMLTextParagraphExport::addTextFrameAttributes: detect invalid anchor
page number; this really should be fixed in Writer/writerfilter though.

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core