Bug: Missing Array.isArray() validation

Bug description

I'm trying to implement a React application for legacy browsers using the @fortawesome/fontawesome-svg-core and @fortawesome/react-fontawesome libraries. However, I came across the following error: 'Unhandled promise rejection TypeError: _hooks[hook].push is not a function'.

While debugging the issue, I traced it back to an attempt to use Array.push() without validating if the object is actually an array. This issue is causing my application to break when I try to run it in older browsers.

The problematic code block is as follows:

  if (plugin.hooks) {
    var hooks = plugin.hooks();
    Object.keys(hooks).forEach(function (hook) {
      if (!_hooks[hook]) {
        _hooks[hook] = [];
      }

      _hooks[hook].push(hooks[hook]);
    });
  }

The solution could be to add a validation:

if(Array.isArray(_hooks[hook])){
   _hooks[hook].push(hooks[hook]);
};

It is present in the following files:

js/all.js, line 4070:1
js-packages@fortawesome\fontawesome-free\js\fontawesome.js, line 1237:1
js-packages@fortawesome\fontawesome-free\js\all.js, line 4070:1
js-packages@fortawesome\fontawesome-free\js\fontawesome.js, line 1237:1
js-packages@fortawesome\fontawesome-svg-core\index.js, line 1237:1
js-packages@fortawesome\fontawesome-svg-core\index.mjs, line 1216:1
js-packages@fortawesome\fontawesome-svg-core\plugins.mjs, line 266:1

Example of error reproduction:

1. Download Firefox 47.0.2;
2. Clone the following repository: vite-react-legacy and open the project;
3. Install the dependencies using the command yarn;
4. Build the project using the command yarn build;
5. Preview the project using the command yarn preview;
6. Open the project in Firefox 47 and you will see the error in the console;
7. Go back to the project and open the file dist\assets\fontawesome-svg-core-legacy-{some random identifier}.js;
8. Add Array validation on line 998:1:

if(Array.isArray(_hooks[hook])){
  _hooks[hook].push(hooks[hook]);
};

1. Run the command yarn preview again and see the project working.

Reproducible test case

https://github.com/uisam00/vite-react-legacy

Screenshots

This is the error:

when i put the validation in the builded file

  if (plugin.hooks) {
    var hooks = plugin.hooks();
    Object.keys(hooks).forEach(function (hook) {
      if (!_hooks[hook]) {
        _hooks[hook] = [];
      }
      if(Array.isArray(_hooks[hook])){
        _hooks[hook].push(hooks[hook]);
      }
    });
  }

The error disappears:

Font Awesome version

6.3.0

Serving

Self-hosted

Implementation

SVG+JS

Browser and Operating System

• Firefox 47.0.2

Web bug report checklist

• I have included a test case because my odds go way up that the team can fix this when I do
• I have searched for existing issues and to the best of my knowledge this is not a duplicate