Fixes #4336

Describe your changes

Better response for invalid JSON

QA Steps

• Run the following POST

POST https://demo.getdkan.org/api/1/datastore/query/cedcd327-4e5d-43f9-8eb1-c11850fa7c55/0 HTTP/1.1

{
  "conditions": [
}

• Confirm you get a 400 error and "Invalid JSON" message
• Run the following POST

POST https://demo.getdkan.org/api/1/datastore/query/cedcd327-4e5d-43f9-8eb1-c11850fa7c55/0 HTTP/1.1

{
    "format": "csv
    "limit": 10
}

• Confirm you get a 400 error and "Invalid JSON" message

Checklist before requesting review

If any of these are left unchecked, please provide an explanation

• I have updated or added tests to cover my code
• I have updated or added documentation