Guard against null response in validation logic

[rushillshah]

Summary

The request validation path can access the response object before confirming it is non-null. Under certain conditions, the response can be null, so validation throws before the null-check path executes.

Impact

Requests that should be handled as validation failures can crash with a null-access error instead.

Expected behavior

Validation should check whether the response exists before reading any response fields or properties.

Suggested fix

Move the null guard ahead of any response access, then add regression coverage for the null-response path.

[rushillshah]

Thanks to @tomthespammer