Reader Profile: Add empty user profile content

[DustyReagan]

Related to pe7F0s-2nU-p2

Proposed Changes

• If a user does not exist, display an empty content message.

Before	After

Why are these changes being made?

• I expect the user profile URL will be directly manipulated often, so having empty content when a user does not exist will improve the user experience.

Testing Instructions

• Use Calypso Live
• Go to a user profile that exists /read/users/1351218 - Confirm it continues to work
• Go to a user profile that does not exist /read/users/1351x218 - Confirm you see the empty content message

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
  • For UI changes, have we tested the change in various languages (for example, ES, PT, FR, or DE)? The length of text and words vary significantly between languages.
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-aUh-p2)?

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-129664

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-129664&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-129664&env=a8c-for-agencies

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

Async-loaded Components (~128 bytes added 📈 [gzipped])

name                                   parsed_size           gzip_size
async-load-calypso-reader-user-stream       +283 B  (+6.8%)     +128 B  (+7.9%)

React components that are loaded lazily, when a certain part of UI is displayed for the first time.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[matticbot]

This PR modifies the release build for the following Calypso Apps:

For info about this notification, see here: PCYsg-OT6-p2

• blaze-dashboard
• command-palette-wp-admin
• help-center
• notifications
• odyssey-stats
• whats-new
• wpcom-block-editor

To test WordPress.com changes, run install-plugin.sh $pluginSlug add/empty-user-profile on your sandbox.

[mehmoodak]

This looks good. Thanks.

[a8ci18n]

This Pull Request is now available for translation here: https://translate.wordpress.com/deliverables/17194365

Some locales (Hebrew, Japanese) have been temporarily machine-translated due to translator availability. All other translations are usually ready within a few days. Untranslated and machine-translated strings will be sent for translation next Monday and are expected to be completed by the following Friday.

Thank you @DustyReagan for including a screenshot in the description! This is really helpful for our translators.