minor cleanup in ScHeaderControl: nCount is always greater than 0
minor cleanup in ScHeaderControl: nCount is always greater than 0

Change-Id: Ia50265e397704131dc948bc2bcbf80a442054b71
Signed-off-by: Rodolfo Ribeiro Gomes <16e015bd1ac6d822a87827be2c0b511db515eae9@gmail.com>
Reviewed-on: https://gerrit.libreoffice.org/6538
Reviewed-by: Markus Mohrhard <17b5858c03a410e5ca9ee070d93f5b34144a17e4@googlemail.com>
Tested-by: Markus Mohrhard <17b5858c03a410e5ca9ee070d93f5b34144a17e4@googlemail.com>

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