Added None check in tree_climber() (closes #22).
Added None check in tree_climber() (closes #22).

RamezIssac/django-sitetree,PukeCloud/django-sitetree,caktus/django-sitetree,ikresoft/django-sitetree,idlesign/django-sitetree,idlesign/django-sitetree,PukeCloud/django-sitetree,RamezIssac/django-sitetree,ikresoft/django-sitetree,caktus/django-sitetree