R闪亮应用程序中的wordcloud错误

Question

当我尝试在Shiny app中绘制wordcloud时出现此错误

"Warning in max(freq) : no non-missing arguments to max; returning -Inf
  Warning: Error in strwidth: invalid 'cex' value" 

这是我的代码，这段代码在server.R

中

library(shiny)
library(quanteda)
library(wordcloud)
require(readtext)

source('helperScript.R')


shinyServer(function(input, output) {


  output$prediction <- renderTable({
    result <- predicted()
    if(! is.null(result))
         p<- predicted()[,1]

  })

  output$plot <- renderPlot({
    result <- predicted()
    wordcloud_rep <- repeatable(wordcloud)

    d <- data.frame(word = result[,1],freq= result[,2])
    wordcloud_rep(words= d$word,freq =d$freq, scale=c(4,0.5),
                  min.freq =1, max.words=50,
                  colors=brewer.pal(8, "Dark2"))
  })

  predicted <- eventReactive(

    #execute with button "Go" clicked, nothing else
    input$go, {

      #Get Input from the UI
      inputTxt <- input$inputTxt

      words <- processInput(inputTxt)
      word1 <- words[1,]
      word2 <- words[2,]
      withProgress({
        setProgress(message = "Processing corpus...")
        predictNextWord(word1, word2)
      })

  })

})