While shiny talking to Drop box, get warning:" Unknown or uninitialised column: 'path'."

Hi, could anyone help me to debug why I couldn' t load/render the table from the Drop Box but could save the input back to it? It also has the warning, and I guess it is highly correlated.

Here is the code I have been trying:

library(shiny)
library(rdrop2)
outputDir <- "responses"


# Define the fields we want to save from the form
fields <- c("name", "used_shiny", "r_num_years")

# Shiny app with 3 fields that the user can submit data for
shinyApp(
  ui = fluidPage(
    DT::dataTableOutput("responses", width = 300), tags$hr(),
    textInput("name", "Name", ""),
    checkboxInput("used_shiny", "I've built a Shiny app in R before", FALSE),
    sliderInput("r_num_years", "Number of years using R",
                0, 25, 2, ticks = FALSE),
    actionButton("submit", "Submit")
  ),
  server = function(input, output, session) {
    
    # Whenever a field is filled, aggregate all form data
    formData <- reactive({
      data <- sapply(fields, function(x) input[[x]])
      data
    })
    
    
    saveData <- function(data) {
      data <- t(data)
      # Create a unique file name
      fileName <- sprintf("%s_%s.csv", as.integer(Sys.time()), digest::digest(data))
      # Write the data to a temporary file locally
      filePath <- file.path(tempdir(), fileName)
      write.csv(data, filePath, row.names = FALSE, quote = TRUE)
      # Upload the file to Dropbox
      drop_upload(filePath, path = outputDir)
    }
    
    loadData <- function() {
      # Read all the files into a list
      filesInfo <- drop_dir(outputDir)
      filePaths <- filesInfo$path
      data <- lapply(filePaths, drop_read_csv, stringsAsFactors = FALSE)
      # Concatenate all data together into one data.frame
      data <- do.call(rbind, data)
      data
    }
    
    # When the Submit button is clicked, save the form data
    observeEvent(input$submit, {
      saveData(formData())
    })
    
    # Show the previous responses
    # (update with current response when Submit is clicked)
    output$responses <- DT::renderDataTable({
      input$submit
      loadData()
    })     
  }
)