router.query is empty for dynamic url without any additional query params

[dnbkr]

Bug report

Describe the bug

When I have a dynamic url, if you visit the URL directly and without a trailing query string in the url, the query params are empty. If you access the page via a next-link, it works as expected.

To Reproduce

Steps to reproduce the behavior, please provide code snippets or a repository:

1. Clone the reproduction example
2. Start the dev server: yarn next dev
3. Visit localhost:3000 and click the link to go to /helloWorld
4. The page outputs the contents of router.query as expected
5. Refresh the page and notice that router.query is empty
6. Go to localhost:3000/helloWorld?anything=whatever
7. Notice that now router.query.foo is populated correctly
8. Look at the second commit to see the diff between the generated create-next-app boilerplate and the implementation

Expected behavior

router.query should be populated with the url param

System information

• OS: macOS
• Browser (if applies) Chrome
• Version of Next.js: 9.5.3
• Version of Node.js: 12.16.1

Additional context

My use case is to build static sites; I don't use 'app' output from next at all, only the output from next export. I use dynamic urls when I have multiple pages that use the same basic structure but different content. this is why the example commit includes the exportPathMap and getStaticRoutes functions.

[dnbkr]

This was converted from an issue to a discussion, which I don't think is accurate - not sure if anyone is able to explain more on why it was classed as not-an-issue?

If I'm using the router wrong in some way then it would be handy to know in what way my understanding is wrong, but the fact that is works as I expected it to when you add in a random query param makes this look more like a bug than a misunderstanding...