Bugfix: CFS file handles can be 0
Bugfix: CFS file handles can be 0

arurke/contiki,arurke/contiki,bluerover/6lbr,arurke/contiki,MohamedSeliem/contiki,arurke/contiki,bluerover/6lbr,MohamedSeliem/contiki,bluerover/6lbr,MohamedSeliem/contiki,bluerover/6lbr,bluerover/6lbr,arurke/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,arurke/contiki,bluerover/6lbr,arurke/contiki,bluerover/6lbr