Fix #15: Set orientation to None if it cannot be determined
Fix #15: Set orientation to None if it cannot be determined

gareth8118/spreads,adongy/spreads,gareth8118/spreads,DIYBookScanner/spreads,miloh/spreads,nafraf/spreads,adongy/spreads,jbaiter/spreads,adongy/spreads,gareth8118/spreads,nafraf/spreads,DIYBookScanner/spreads,jbaiter/spreads,jbaiter/spreads,DIYBookScanner/spreads,nafraf/spreads,miloh/spreads,miloh/spreads