Validate request fields in sql_json API

[EugeneTorap]

We use postman/insomnia http client to call/test all superset API.
And we found that /superset/sql_json/ API don't have validation for required fields. For example if we don't provide sql field in JSON body of request we get such error: "message": "Failed to execute query '164' - 'None': 'NoneType' object has no attribute 'strip'" and then Query History record is created with sql column is null (db table - query)

How to reproduce the bug

1. Call login API to auth
2. Call /superset/sql_json/ API without sql field
3. See response error
4. See error for /api/v1/query/ API

Expected results

We have to validate required fields for /superset/sql_json/ API .

Actual results

There's no validation for /superset/sql_json/ API .
Columns sql has null value in db table - query.
/api/v1/query/ API is broken with error message is "error": "'NoneType' object has no attribute 'strip'"

Screenshots

Environment

(please complete the following information):

• browser type and version:
• superset version: superset version
• python version: python --version
• node.js version: node -v
• any feature flags active:

Checklist

Make sure to follow these steps before submitting your issue - thank you!

• I have checked the superset logs for python stacktraces and included it here as text if there are any.
• I have reproduced the issue with at least the latest released version of superset.
• I have checked the issue tracker for the same issue and I haven't found one similar.

Additional context

Add any other context about the problem here.
@michael-s-molina @kgabryje @codyml @zhaoyongjie @diegomedina248 @jinghua-qa @geido @AAfghahi @srinify