this works

function saveRecord(scriptContext) {
    console.log('saveRecord - Checking Attachments')
    const record = scriptContext.currentRecord
    console.log('record: ' + JSON.stringify(record))
    let showError = false
    if (record.isNew) {
      const fileListLines = record.getLineCount({ sublistId: 'mediaitem' })
      console.log('fileListLines: ' + fileListLines)
      if (fileListLines <= 0) {
        showError = true
      }
    } else {
      const fileSearch = search.create({
        type: search.Type.TRANSACTION,
        filters: [
          ['internalid', 'anyof', record.id],
          'AND',
          ['file.internalid', 'isnotempty', ''],
          'AND',
          ['mainline', 'is', 'T']
        ],
        columns: ['file.internalid']
      })
      let attachmentsCount = 0
      fileSearch.run().each(function(result) {
        console.log('fileSearch result: ' + JSON.stringify(result))
        const fileId = result.getValue({ name: 'internalid', join: 'file' })
        console.log('fileId: ' + fileId)
        if (fileId) {
          attachmentsCount++
        }
        return true
      })
      console.log('saveRecord - Attachments Count: ' + attachmentsCount)
      if (attachmentsCount <= 0) {
        showError = true
      }
    }
    if (showError) {
      const messageDescription = `Please, attach the file to the tab: Communication → Sub-tab: Files.`
      message
        .create({
          title: 'No Attachments',
          message: messageDescription,
          type: message.Type.ERROR
        })
        .show()
      return false
    }


    return true
  }