fix bug with keyphrase_graph which has no lonely keyphrase

Signed-off-by: pntruongan <pntruongan@pnta-laptop.localdomain>
Merge branch 'master' of ssh://git@github.com/cntn02/Semantic-document-base.git
backup database


Signed-off-by: pntruongan <pntruongan@pnta-laptop.localdomain>
debugging on a nasty bug when searching "data structure algorithm"

Signed-off-by: pntruongan <pntruongan@pnta-laptop.localdomain>
backup database

Signed-off-by: pntruongan <pntruongan@pnta-laptop.localdomain>