How to use the numeral.nullFormat function in numeral

HDG,
  MAX_ZOOM,
  MIN_ZOOM,
  EXTENSION_LINE_OFF,
  EXTENSION_LINE_2_MIN,
  EXTENSION_LINE_5_MIN,
  EXTENSION_LINE_10_MIN
} from './enums'
import Map from './map'
import Ais from './ais'
import Connection from './data-connection'
import {toNauticalMiles} from './utils'
import InstrumentConfig from './instrument-config'
import fullscreen from './fullscreen'
import {settings, clearSettingsFromLocalStorage} from './settings'
numeral.nullFormat('N/A')
fullscreen(settings)

const drawObject = Atom({distance: 0, del: false})
const connection = Connection({providers: settings.get().data, settings})

const Controls = ({settings, connectionState}) => {
  return (
    <div>
      <div>
         settings.view(L.prop('showMenu')).modify(v =&gt; !v)}
        /&gt;
      </div></div>

import chroma from "chroma-js";
import _ from "lodash";
import numeral from "numeral";

import { measureText } from "./MeasureText";
import { buildStyling } from "./dataViewerMenuUtils";

const IDX = "dtale_index";
const DEFAULT_COL_WIDTH = 70;

numeral.nullFormat("");

function isStringCol(dtype) {
  return _.some(["string", "object", "unicode"], s => dtype.startsWith(s));
}

function isIntCol(dtype) {
  return dtype.startsWith("int");
}

function isFloatCol(dtype) {
  return dtype.startsWith("float");
}

function isDateCol(dtype) {
  return _.some(["timestamp", "datetime"], s => dtype.startsWith(s));
}