Mathia sending percentCorrect: null, not expected

[danoswaltCL]

Version where bug was found:
6, but it's not really an upgrade issue? I believe this has been happening since the metrics connector data faucet was reconnected a month or so back.

Describe the bug
Logs from data connector occasionally are sending null for percentCorrect. This results in a 400 bad request. The net effect may hopefully just noise though, because every request that prompts this error only has this one metric attached, so I don't know if we are losing anything we wanted to keep in the first place?

{
            "userId": "64b20e3f-0e99-4a09-b47f-b3f478824d65",
            "value": [
                {
                    "metrics": {
                        "attributes": {
                            "percentCorrect": null <----- Upgrade expects a string or number for an attribute
                        },
                        "groupedMetrics": []
                    },
                    "timestamp": "2024-11-30T00:23:10.044Z"
                }
            ]
        }
        ```

**Expected behavior**
I'm not sure we should be expecting null, so this feels like a correct behavior for UpGrade.

[danoswaltCL]

@msandbothe is out I guess now, @amurphy-cl who else might be a contact / channel for data that is getting piped over?