make sure we don't export shapes with negative size (fixes n#760997)
make sure we don't export shapes with negative size (fixes n#760997)

Change-Id: Id77cbfaa287d15c4af9a91976f3b091e68229223

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