Custom Routes must return an array

Why This Error Occurred

When defining custom routes an array wasn't returned from either headers, rewrites, or redirects.

Possible Ways to Fix It

Make sure to return an array that contains the routes.

Before

next.config.js

module.exports = {
  async rewrites() {
    return {
      source: '/feedback',
      destination: '/feedback/general',
    }
  },
}

After

next.config.js

module.exports = {
  async rewrites() {
    return [
      {
        source: '/feedback',
        destination: '/feedback/general',
      },
    ]
  },
}