Bugfix: don't force URL validation if a file is provided.

[rebeccacremona]

We recently made a change to Perma's URL validation behavior: we used to validate URLs locally, but now we send the URLs to the Scoop API for validation.

When I added the new code, I missed two important lines. We are not supposed to validate the URL, if making a Perma Link from an upload instead of from a capture.

It turns out that our tests of the upload-your-own functionality use the same URL every time... a valid one.

So, this PR does two thing:

• add back the missing if not uploaded_file:, and
• add a regression test

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (3523e14) 71.21% compared to head (a3202e2) 71.22%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #3474 +/- ## ======================================== Coverage 71.21% 71.22% ======================================== Files 48 48 Lines 6494 6495 +1 ======================================== + Hits 4625 4626 +1 Misses 1869 1869 ```

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[sentry-io[bot]]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ ScoopAPINetworkException /api/v1/user/archives/ View Issue

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