Onboarding: failure to redirect user to the editor.

### Quick summary

In CI, it was observed (at least once) that after selecting the writing intent, the stepper failed to redirect the user to the editor.

### Steps to reproduce

1. sign up as an existing user.
2. initiate the new site creation flow, skip domain selection, select a free plan, and continue.
3. select the Write & Publish intent.
4. fill in blog name and tagline and continue.

For internal details like site id, see the Logs/Notes section below.

### What you expected to happen

User is redirected to the editor.

### What actually happened

User is redirected to a white screen of death.

URL at the time of failure: `https://wordpress.com/post/?showLaunchpad=true`

**Screenshot**

**Video**

https://github.com/Automattic/wp-calypso/assets/6549265/d3222f13-41c9-40c7-899c-d13b332ffd74

### Impact

Some (< 50%)

### Available workarounds?

Yes, difficult to implement

### Platform (Simple and/or Atomic)

_No response_

### Logs or notes

site id: 222246322
user id: 237707803

Start by reproducing the onboarding flow through the Write & Publish intent and inspect the stepper transition to /post/?showLaunchpad=true. Use the supplied site and user IDs with the logs and video to identify why the editor becomes a white screen. Done means the flow reliably redirects the user to the editor instead of the white screen.

Written by the indexing model from the issue text.