title: The "file" argument must be of type string. Received type undefined on npm run deploy to gh-pages
body: <p>I was trying to deploy a react application to gh-pages. I've done it before, but this is the first time I'm getting this kind of error. It says</p>
  
  <p>The "file" argument must be of type string. Received type undefined</p>
  
  <p>I tried removing the node_modules folder and reinstalled all the packages with npm install, but still finding the same error</p>
  
  <p>Below is my package.json file</p>
  
  <pre><code>{
        "name": "qrummy",
        "version": "0.1.0",
        "homepage": "https://quiph.github.io/QRummy/",
        "private": true,
        "dependencies": {
          "firebase": "^6.2.4",
          "gh-pages": "^2.1.0",
          "react": "^16.8.6",
          "react-dom": "^16.8.6",
          "react-scripts": "3.0.1"
        },
        "scripts": {
          "start": "react-scripts start",
          "build": "react-scripts build",
          "test": "react-scripts test",
          "predeploy": "npm run build",
          "deploy": "gh-pages -d build",
          "eject": "react-scripts eject"
        },
        "eslintConfig": {
          "extends": "react-app"
        },
        "browserslist": {
          "production": [
            "&gt;0.2%",
            "not dead",
            "not op_mini all"
          ],
          "development": [
            "last 1 chrome version",
            "last 1 firefox version",
            "last 1 safari version"
          ]
        }
      }
  </code></pre>
  
  <p>And this is my main index.js file</p>
  
  <pre><code>import React from 'react';
  import ReactDOM from 'react-dom';
  import './index.css';
  import App from './App';
  import * as serviceWorker from './serviceWorker';
  
  ReactDOM.render(&lt;App /&gt;, document.getElementById('root'));
  
  // If you want your app to work offline and load faster, you can change
  // unregister() to register() below. Note this comes with some pitfalls.
  serviceWorker.unregister();
  </code></pre>
  
  <p>Error Output is as follows</p>
  
  <pre><code> qrummy@0.1.0 deploy /home/qtalkdev/Krunal/github/QRummy
  &gt; gh-pages -d build
  
  The "file" argument must be of type string. Received type undefined
  npm ERR! code ELIFECYCLE
  npm ERR! errno 1
  npm ERR! qrummy@0.1.0 deploy: `gh-pages -d build`
  npm ERR! Exit status 1
  npm ERR! 
  npm ERR! Failed at the qrummy@0.1.0 deploy script.
  npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
  
  npm ERR! A complete log of this run can be found in:
  npm ERR!     /home/qtalkdev/.np`enter code here`m/_logs/2019-08-01T17_28_14_611Z-debug.log
  </code></pre>