The bundled web vault (2026.6.4) requires seven query parameters in the
accept-organization URL and rejects the invite client-side when any of them is
null, showing only "Unable to accept invitation" without sending a request to
the server.
send_invite() never appended initOrganization, and appended
orgUserHasExistingUser only for users who already had an account, so every
organization invitation e-mail produced a link that could not be accepted.
Web vault 2026.4.1 (shipped with 1.36.0) read these parameters null-safely,
which is why this only appeared in 1.37.0.
Fixes#7481
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
