Login redirects to `/account/complete/_xxxx` with raw JSON error

### Current Behavior

After a period of not logging in to FF, I am redirected to `/account/complete/_xxxx` and shown an error in raw JSON:


### Expected Behavior

Should log in so long as user name/password (SSO) was correct, otherwise redirect accordingly.

### Steps To Reproduce

not sure how to reproduce (I tried editing various parts of cookies, storage to mimic it) but for my 3 encounters, it was always upon login after 8 days of not logging in to FFC

### Environment

- FlowFuse version: FFC current (2.11.0 as of writing)
- Node.js version:
- npm version:
- Platform/OS: Win 11
- Browser: Chrome latest

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate