Fixes #10427

To test:

Testing on release build version

1. Sign Up For WordPress.
2. Once you have reached the New Account screen, ensure you have a short Display Name of three letters or less.
3. click the username control.
4. The error should then appear with a query instead of null.

Testing using the debug app.

1. Utilize the testing steps to modify code from this PR so that you are able to reach the new account screen from the login page since during development the app can't access signup functionality.
2. Follow steps 2 to 4 from above.

Below is an example where I used a single letter j as my display name and it's shown instead of null

Update release notes:

• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.