fdo#74479: Treat empty cells as if they have a value of 0.
fdo#74479: Treat empty cells as if they have a value of 0.

Change-Id: I3701848016c230138e8791f683a2c8b97219198d

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