[HELP] It seems that tickscript makes data stay in cache

Hi, I'm writing a script but I notice some peculiar behaviors:

```
var data = batch
|query('''
SELECT * FROM "my_db"."autogen"."measurements_id" WHERE "param1" = '...' AND "param2" = '...'
''')
.period(3m)
.every(20s)
|log()
|httpOut('query')

var trigger = data
|stats(25s)
|log()
|httpOut('stats')
|alert()
.crit(lambda: "emitted" == 0.0)
```

If, when it starts, I don't have data for that measurement, it correctly makes an alert and closes it at the first measurement received, but once the period has passed (so I expect that the query has no results) it continues to visualize the last measurement.
(I saw it by doing a get on the HttpOut endpoint)

In addition, the output of stats (emitted) grows at each execution

Where am I going wrong?

Start by reproducing the supplied Tickscript with the batch query, stats, httpOut, and alert nodes. Inspect the query results after the three-minute period and compare the emitted value across executions. Done means the cause of the retained measurement and growing emitted count is identified and the issue has a clear corrective scope.

Written by the indexing model from the issue text.