gatsby: [Firefox] Unhandled promise rejection TypeError: "this.loadPageDataJson(...).then(...).finally is not a function

Description

When I run in localhost works ok with all the browsers including Firefox but when it goes to production the Firefox v68.0.1 looks misaligned caused (I guess) for this .finally function.

Steps I tried

I tried to use "gatsby-plugin-compile-es6-packages": "^2.1.0" to compile es6 features like they are using in #2177 but without luck.

Also I tried:

exports.modifyWebpackConfig = ({ config, stage }) => {
  switch (stage) {
      case "build-javascript":
          const app = config._config.entry.app;
          config._config.entry.app = [require.resolve("./polyfills"), app];

          break;
      default:
          break;
  }

  return config;
};

Expected result

What should happen?

Works ok with Chrome (v75.0.3770.142).

Actual result

Returns a console error which for what I found it’s something that .finally() function is quite new and maybe is not fully supported yet.

Unhandled promise rejection TypeError: 
"this.loadPageDataJson(...).then(...).finally is not a function"

How it looks like in Firefox (v68.0.1)

Also I’m using "antd": "^3.12.3" package to handle the UI and in this CSS class if you change flex-direction: column to row it looks ok but the error still persists.

.ant-layout {
    display: flex;
    flex: auto;
    flex-direction: column;
    min-height: 0;
    background: #f0f2f5;

Environment

System:
    OS: macOS 10.14.5
    CPU: (8) x64 Intel(R) Core(TM) i7-4770HQ CPU @ 2.20GHz
    Shell: 5.3 - /bin/zsh
  Binaries:
    Node: 10.16.0 - /usr/local/bin/node
    Yarn: 1.16.0 - /usr/local/bin/yarn
    npm: 6.9.0 - /usr/local/bin/npm
  Languages:
    Python: 2.7.10 - /usr/bin/python
  Browsers:
    Chrome: 76.0.3809.87
    Firefox: 68.0.1
    Safari: 12.1.1
  npmPackages:
    gatsby: ^2.0.76 => 2.13.45
    gatsby-image: ^2.0.20 => 2.2.7
    gatsby-mdx: 0.6.3 => 0.6.3
    gatsby-plugin-antd: ^2.0.2 => 2.0.2
    gatsby-plugin-compile-es6-packages: ^2.1.0 => 2.1.0
    gatsby-plugin-google-analytics: ^2.0.9 => 2.1.6
    gatsby-plugin-less: ^2.0.8 => 2.1.2
    gatsby-plugin-manifest: ^2.0.9 => 2.2.4
    gatsby-plugin-offline: ^2.0.16 => 2.2.4
    gatsby-plugin-react-helmet: ^3.0.2 => 3.1.2
    gatsby-plugin-react-svg: ^2.1.1 => 2.1.1
    gatsby-plugin-sass: (internal URL) => 2.0.11
    gatsby-plugin-sharp: ^2.0.18 => 2.2.9
    gatsby-plugin-web-font-loader: ^1.0.4 => 1.0.4
    gatsby-remark-autolink-headers: ^2.0.14 => 2.1.3
    gatsby-remark-copy-linked-files: ^2.0.8 => 2.1.4
    gatsby-remark-images: ^3.0.1 => 3.1.7
    gatsby-source-filesystem: ^2.0.25 => 2.1.7
    gatsby-source-git: ^1.0.1 => 1.0.1
    gatsby-source-graphql: ^2.0.8 => 2.1.3
    gatsby-transformer-remark: ^2.2.4 => 2.6.10
    gatsby-transformer-sharp: ^2.1.8 => 2.2.5
  npmGlobalPackages:
    gatsby-cli: 2.7.9