Fix for engine routes (2)

[blocknotes]

Hey @k0kubun.
I still have issues with an application with Rails engines... but it's tricky to create a spec for the case 😑

That's what I see:

• with the current master version (0.47) I get again "No route matched for ..." exception;
• applying the PR change to find_rails_route (but keeping the raise line) it gets better, but it still fails when there's a test on a non-existing path;
• replacing the raise with the warn seems to solve the issue completely.

I think that the iteration of the routes with the current code still returns nil in some situations (probably the line return find_rails_route(request, app: route.app.app, fix_path: false)).

Think about it, if you don't feel confident to merge a PR without a good test it's ok (in any case having an alternative here could help someone else perhaps).

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Relates to #38 and #37

[k0kubun]

If you can't create a test case, please at least share a repository that reproduces it. You should at least have that one somewhere, and I think you can carve out what's still reproducing your issue to a small repository. Think about it, if I have no way to test my own code, it will randomly reproduce the same issue on your project again. So merging it temporarily doesn't mean anything if I can't reproduce it.

[blocknotes]

If you can't create a test case, please at least share a repository that reproduces it. You should at least have that one somewhere, and I think you can carve out what's still reproducing your issue to a small repository. Think about it, if I have no way to test my own code, it will randomly reproduce the same issue on your project again. So merging it temporarily doesn't mean anything if I can't reproduce it.

I tried to isolate the behaviour without success and the project is closed source.
It's fine anyway - I'll keep the commit in my fork.