Unable to add two fields together

from(bucket: "mybucket")
|> range(start: 2023-07-25T00:00:00Z, stop: 2023-07-26T00:00:00Z)
|> filter(fn: (r) => r._field == "Power(W)" or r._field == "system_production")
|> pivot(rowKey:["_time"], columnKey: ["_field"], valueColumn: "_value")
|> map(fn: (r) => ({
_time: r._time,
system_production: int(v: r["system_production"]),
total_solar_generation: int(v: r["Power(W)"]) + int(v: r["system_production"])
}))

I have two solar inverters. One shows generation as "system production" and the other shows as "power". I'm trying to add these two together to create a new value called "total solar generation" - every time i run this or slight variations, i end up with Null in the data explorer. please help!!

Start by reproducing the supplied Flux query in the InfluxDB Data Explorer, focusing on the pivot and map steps that produce null values. No repository file or test is identified; done would mean determining why the two fields cannot be combined and documenting or implementing a confirmed fix.

Written by the indexing model from the issue text.