in https://raw.githubusercontent.com/screeps/engine/c318a920e3c04c1285c885e328d89ef748d7004c/src/game/creeps.js line 608 I think

            if(data(target.id)[resourceType] || data(target.id)[resourceType] < amount) {
                return C.ERR_NOT_ENOUGH_RESOURCES;
            }

should read

            if(!data(target.id)[resourceType] || data(target.id)[resourceType] < amount) {
                return C.ERR_NOT_ENOUGH_RESOURCES;
            }