Power Apps: Fetching data from SQL server with "Power Automate" does not store null values in collection

Question

I am currently developing an application in Microsoft Power Apps. I fetch some data from my SQL Server using PowerAutomate. My Flow executes a stored procedure and it returns my data successfully. As you can see here:

{
"statusCode": "200",
"body": [
    {
        "Id": 6,
        "Beschreibung": "test",
        "Erstelldatum": "2022-03-09T11:00:21.708",
        "Zieldatum": null,
        "Erledigungskommentar": null,
        "Titel": "test",
        "ErstellerId": "xyz",
        "Prioritaet": 3,
        "Ort": "test",
        "Ticketstatus": 1,
        "Fehlercode": null,
        "Abteilung": 1,
        "Rueckfrage_Von": null
    },
    {
        "Id": 7,
        "Beschreibung": "testtttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttt",
        "Erstelldatum": "2022-03-09T11:30:31.654",
        "Zieldatum": "2022-03-15T00:00:00",
        "Erledigungskommentar": null,
        "Titel": "test",
        "ErstellerId": "xyz",
        "Prioritaet": 3,
        "Ort": "tetet",
        "Ticketstatus": 1,
        "Fehlercode": 1,
        "Abteilung": 1,
        "Rueckfrage_Von": null
    }
]

}

BUT: When I call this flow in my OnVisible attribute on my power apps screen, it fetches the data but ignores the whole attributes that are nullable (can contain null values).

You can see here on the picture, that the columns "Zieldatum", "Rueckfrage_Von", and "Fehlercode" are not in the collection and I cannot access them:attributes of my collection

Has somebody an idea how I can enable that also nullable attributes get stored in my collection? THANK YOU!