Completions for flux record not working

__Steps to reproduce:__
List the minimal actions needed to reproduce the behavior.

1. enter query editor within data filter on data that has records
```
from(bucket: "bucket1")
|> range(start: v.timeRangeStart, stop: v.timeRangeStop)
|> filter(fn: (r) => r["_measurement"] == "procstat")
|> filter(fn: (r) => r.) // <---- COMPLETIONS NOT Shown accurately
|> aggregateWindow(every: v.windowPeriod, fn: mean, createEmpty: false)
|> yield(name: "mean")
```


for the above you don't get any completions. When that filter is changed to `filter(fn: (r) => r` you will receive the following and the `r` object is not listed:


__Expected behavior:__
Expected to get `r` in the completions before the `.` and get its properties once I enter the dot.

__Actual behavior:__
no completions are provided

__Environment info:__

* System info: `Darwin 18.7.0 x86_64`
* Influxd version: master(b12c3ef77b)
* Browser: FireFox 79.0

Start in the query editor within the data filter and reproduce the issue using the Flux query from the report. Check completion behavior at `r` and `r.`; done means `r` appears before the dot and its properties appear after entering the dot.

Written by the indexing model from the issue text.