x/telemetry/godev: telemetry.go.dev chart view is broken

[hyangah]

https://telemetry.go.dev/charts/2024-05-07

It was broken from 05/07 because the worker produces chart json file with unexpected Charts in it.

{
    "DateRange": [
        "2024-05-13",
        "2024-05-13"
    ],
    "Programs": [
        {
            "ID": "charts:cmd/compile",
            "Name": "cmd/compile",
            "Charts": [
                null,
                null,
                null,
                null,
                null
            ]
        },
        {
            "ID": "charts:cmd/go",
            "Name": "cmd/go",
            "Charts": [
                null,
                null,
                null,
                null,
                null,
                null
            ]
        },
        ...

And, that caused https://go.googlesource.com/telemetry/+/refs/heads/master/internal/content/telemetrygodev/charts.ts#41 failed.

[gopherbot]

Change https://go.dev/cl/585479 mentions this issue: godev/cmd/worker: skip empty partition in charts