TickScript deadman groupby nil value

Hi all, I have a strange problem with the deadman type alert. I defined a groupby condition on a tag that by the time the script is deployed the data hasn't arrived yet, so a "nil" error is thrown. Is there a way to ignore when the bucket is empty and not throw this kind of error?
This is the current script:
```
var db = 'test-db'

var rp = 'test-rp'

var measurement = 'my-test'

var groupBy = ['unique-field']

var whereFilter = lambda: ("condition" == 'false') AND ("description" == 'my-desc')

var period = 1m

var name = 'Dead-unique'

var idVar = name + '-{{.Group}}'

var message = ''

var idTag = 'alertID'

var levelTag = 'level'

var messageField = 'message'

var durationField = 'duration'

var outputDB = 'alarms-db'

var outputRP = 'alarms-rp'

var outputMeasurement = 'alerts'

var triggerType = 'deadman'

var threshold = 0.0

var data = stream
|from()
.database(db)
.retentionPolicy(rp)
.measurement(measurement)
.groupBy(groupBy)
.where(whereFilter)

var trigger = data
|deadman(threshold, period)
.message(message)
.id(idVar)
.idTag(idTag)
.levelTag(levelTag)
.messageField(messageField)
.durationField(durationField)
.stateChangesOnly()

trigger
|eval(lambda: "emitted")
.as('value')
.keep('value', messageField, durationField)
|eval(lambda: float("value"))
.as('value')
.keep()
|influxDBOut()
.create()
.database(outputDB)
.retentionPolicy(outputRP)
.measurement(outputMeasurement)
.tag('alertName', name)
.tag('triggerType', triggerType)

trigger
|httpOut('output')

```

and this is the error with nil value:
```JSON
{
"id": "Dead-unique-nil",
"message": "",
"details": "....",
"duration": 0,
"level": "CRITICAL",
"data": {
"series": [
{
"name": "stats",
"columns": [
"time",
"emitted"
],
"values": [
[
"2023-03-13T11:01:00Z",
0
]
]
}
]
},
"previousLevel": "OK",
"recoverable": true
}
```

Start by reproducing the supplied TickScript with an empty group-by tag, focusing on the from().groupBy() and deadman() entry points. Determine whether a nil group can be ignored without changing alert output, then verify that deployment succeeds and no Dead-unique-nil alert is emitted for the empty bucket.

Written by the indexing model from the issue text.