old_contents: import { select } from 'd3-selection'
  
  export function ensureData(d, i) {
    if (!d) select(this).datum([])
  }
  
new_contents: import { select } from 'd3-selection'
  
  export function ensureData(d, i) {
    let rows = d || []
    rows.rows = null
    select(this).datum(rows)
  }
  
subject: Fix stale data: Encapsulate initial pre-processed row cleanup.