Fix crash with fdo60063-1.docx
Fix crash with fdo60063-1.docx

Compared to the original version, this one tries hard
not to produce empty keywords.

Change-Id: I11d036c2d54cde2d3c311a77c115011246f38d0a
Reviewed-on: https://gerrit.libreoffice.org/4091
Reviewed-by: Fridrich Strba <cc5239b4c84e795cbd430bca0f77cadba002516f@documentfoundation.org>
Tested-by: Fridrich Strba <cc5239b4c84e795cbd430bca0f77cadba002516f@documentfoundation.org>

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