Wrong status code for a nonexisting material id

[BeatBioInfo]

Steps to reproduce
Create a collection on Postman
Click on the “add request” button
Use the POST method to call a request http://qa-school-test-api.quantori.academy/api/v1/session
Enter the following “string” in the “Body” in the following order
• {
“username”: “admin”,
“password”: “1234”
}
Press the “send” button to generate an “accessToken”.
Click “Add request” to call a 'non-existing material id' in a course
Use the GET method to call a request {{Host}}api/v1/courses/3093/materials/200
No needed “string” in the “Body”

Actual behaviour
• Status code: 200; Ok
Body Response: "Null" in the body

Expected ### behaviour
• Status code: 404 Not found
Body Response: "Enter a valid material id"

Screenshots
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Screenshots
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