Fix parsing of 'channel interfering'.
Fix parsing of 'channel interfering'.

Off-by-one in error checking.  Reported by Gioacchino Mazzurco.

tcatm/babeld,Gwendocg/babeldToS,jech/babeld,jech/babeld,sudomesh/babeld,Gwendocg/babeldToS,Drooids/babeld,wlanslovenija/babeld,woniullb/babeld,boutier/babeld,wlanslovenija/babeld,dtaht/babeld-shortrtt-metrics