DROP SERIES in FLUX

I need to remove series that contain a _value of zero. Is that possible?

From my previous question, here are the details of what caused the issue:

|> aggregateWindow(every: 10s, fn: mean)  
|>fill(column: "_value", usePrevious: true)

After filling forward using Previous, I often end up with null values at the beginning of my data table. I would like to remove those first few rows. How can I do that?