insights: Return more helpful error message when `createLineChartSearchInsight` is called without series

Created by: CristinaBirkel

Running this query:

mutation {
    createLineChartSearchInsight (input: {
        options: {
            title: "test response no dashboard"
        },
        dataSeries: []
    })
    {
        view { id }
    }
}

Returns this error:

{
  "errors": [
    {
      "message": "insight not found",
      "path": [
        "createLineChartSearchInsight",
        "view"
      ]
    }
  ],
  "data": null
}

If we want to have the constraint that insight views must be created with at least one series, a more helpful error message here would be nice.

Note: This also applies to updateLineChartSearchInsight as well.

CreateLineChartSearchInsight mutation UpdateLineChartSearchInsight mutation