Material with data which contains spaces only shouldn't be added into the course

[Tatyana-Kravchenko]

Steps to reproduce
Teacher added new material in his course (courseId: {{courseIdForMaterials}})
Post {{host}}/api/v1/courses/{{courseIdForMaterials}}/materials
Body Request
{
"title": "QA school{{categoryPostfix}}",
"data": " ",
"order": 2
}
Tests
pm.test("Status code is 400", function () {
pm.response.to.have.status(400);
});

pm.test("Response time is less than 1000ms", function () {
pm.expect(pm.response.responseTime).to.be.below(1000);
});

pm.test("Check the error message is correct", function () {
const jsonData = pm.response.json();
pm.expect(jsonData.errors[0].msg).equal("You are not allowed to use spaces only")
});
Actual behavior

1. Status code is 200
2. Response time is less than 1000 ms
3. New material with data which contains spaces only was added
   Expected behavior
4. Status code is 400
5. Response time is less than 1000 ms
6. New material with data which contains spaces only wasn't added
7. The error text ("You are not allowed to use spaces only") is correct
   Screenshots
   If applicable, add screenshots to help explain your problem.