make Settings.getDefaultNavigationTool() more tolerant (fix #8069)
make Settings.getDefaultNavigationTool() more tolerant (fix #8069)

cgeo/cgeo,rsudev/c-geo-opensource,tobiasge/cgeo,auricgoldfinger/cgeo,S-Bartfast/cgeo,S-Bartfast/cgeo,tobiasge/cgeo,matej116/cgeo,auricgoldfinger/cgeo,tobiasge/cgeo,rsudev/c-geo-opensource,matej116/cgeo,cgeo/cgeo,S-Bartfast/cgeo,matej116/cgeo,cgeo/cgeo,auricgoldfinger/cgeo,cgeo/cgeo,rsudev/c-geo-opensource