Use of maxunmeasuredbw and bwweightscale is broken in consensus

While refactoring, I noticed this code in dirvote.c:

    if (params) {
      if (strcmpstart(params, "bwweightscale=") == 0)
        bw_weight_param = params;
      else
        bw_weight_param = strstr(params, " bwweightscale=");
    }

    if (bw_weight_param) {
      int ok=0;
      char *eq = strchr(bw_weight_param, '=');
      if (eq) {
        weight_scale = tor_parse_long(eq+1, 10, 1, INT32_MAX, &ok,
                                         NULL);
        if (!ok) {
          log_warn(LD_DIR, "Bad element '%s' in bw weight param",
              escaped(bw_weight_param));
          weight_scale = BW_WEIGHT_SCALE;
        }
      } else {
        log_warn(LD_DIR, "Bad element '%s' in bw weight param",
            escaped(bw_weight_param));
        weight_scale = BW_WEIGHT_SCALE;
      }
    }

Looking at the use of tor_parse_ulong(). Since "next" is NULL, any unconverted characters should make it give an error, making us use the default value.