[FIX]correct a small bug when creating odometer with value zero

bzr revid: csn@openerp.com-20121107151726-xr6754fd9t39k5zc

addons/fleet/fleet.py

@@ -102,6 +102,8 @@ class fleet_vehicle_cost(osv.Model):
             data['vehicle_id'] = contract.vehicle_id.id
             data['cost_subtype'] = contract.cost_subtype.id
             data['cost_type'] = contract.cost_type
+        if 'odometer' in data and not data['odometer']:
+            del(data['odometer'])
         return super(fleet_vehicle_cost, self).create(cr, uid, data, context=context)