Mistral adapter error handling: Improve object validation and error messages for nested content

[ingo-eichhorst-ionos]

Before submitting your bug report

• I believe this is a bug. I'll try to join the Continue Discord for questions
• I'm not able to find an open issue that reports the same bug
• I've seen the troubleshooting guide on the Continue Docs

Relevant environment info

- OS: MacOS 15.2 (24C101) - M1 (ARM)
- Continue version: 0.9.251
- IDE version: VS Code - Version: 1.96.2 (Universal)
- Model: GPT-4o

- config.json:
  
  "models": [
    {
      "title": "codestral",
      "model": "codestral-latest",
      "provider": "mistral",
      "apiKey": "random_string"
     }  ...
  ]

Description

The Mistral adapter for Codestral (And properly other models as well) is not displaying a proper error.
Instead the not very helpful "Cannot read properties of undefined (reading 'content')" is displayed. IMHO the code should handle deep nested objects more gracefully and e.g. display a JSON stringify of the object if the object nesting is different than expected.

To reproduce

1. A mistral model like in the config above with a wrong API-Key.
2. Send any chat request

Log output

##### Completion options #####
{
  "contextLength": 32768,
  "model": "codestral-latest",
  "maxTokens": 4096
}

##### Request options #####
{}

##### Prompt #####
<system>


<user>

[Patrick-Erichsen]

This was a separate issue with our error logging that I believe has been resolved in latest pre-release. Thanks for the +1 on it though!