R shiny ERROR: object of type 'closure' is not subsettable [duplicate2]

Question

Please help me;] What am I subsetting and where am I wrong.The error is certainly the passage with biomaRT, but I do not know where.

My error: Listening on http://127.0.0.1:5836 Warning: Error in [: object of type 'closure' is not subsettable

My code:
ui.R

library(shiny)  library("biomaRt")  


shinyUI(fluidPage(  
  titlePanel("Analiza funkcjonalna dla danych cytogenetycznych"),  
  sidebarLayout(  
    sidebarPanel(    
    fileInput(inputId='plik1', label='Wybierz plik z danymi'),
    tags$hr(),
    checkboxInput(inputId='header', label='Header', value=TRUE),
    tags$hr(),
    radioButtons(inputId = 'sep', label= 'Separator', choices = c(Przecinek=',',Srednik=';',Tab='\t', Spacja=''), selected = ','),
    tags$hr(),
    p("Kliknij w ponizszy przycisk jesli chcesz wykonac analize funkcjonalna wprowadzonych danych"),
    actionButton("act","Kliknij aby wykonac analize")
    ),

    mainPanel(
      uiOutput('tabelazb'),
     dataTableOutput('opracowane')
      )
  )
))

server.R

shinyServer(function(input, output) {

  dane<-reactive({
    folder<-input$plik1
    if(is.null(folder)){return()}
    read.table(file=folder$datapath,sep=input$sep,header = input$header)
  })
  output$tabela1<- renderTable({
    if(is.null(dane())){return()}
    input$plik1
  })
  output$tabelad<-renderTable({
    if(is.null(dane())){return()}
    dane()
  })
  output$opracowane<-renderDataTable({
    input$act
    if(input$act==0)
    {return()}
    else
    {if(is.null(dane()))
    {return()}
      else
      {x=data.frame()
      y=list()
      x=dane[,c("chromosome","position_start","position_stop")]# dodanie nazw kolumn
      y[[1]]=x

      #listMarts()
      z=useMart("ensembl")
      z=useDataset("hsapiens_gene_ensembl",mart=z)
      filtry=listFilters(z)
      #listAttributes(z)
      #Zbieramy wyniki
      b=list()
      g=list()

      for (i in 1:length(y))
      {
        d=as.matrix(y[[i]])
        #name_1006 - go term name
        b[[i]]=getBM(attributes=c("entrezgene","hgnc_symbol", "chromosome_name", "start_position", "end_position","band","description"),filters=filtry[1:3,1],values=list(d[,1],d[,2],d[,3]),mart=z)


        Na=which(b[[i]][,1] %in% NA == TRUE)
        if (length(Na) >= 1)
        {
          b[[i]] <- b[[i]][-c(Na),]
        }
      }}
    }
  })
  output$tabelazb<-renderUI({
    if(is.null(dane()))
    {h5(helpText("Brak wczytanego pliku"))}
    else
    {tabsetPanel(tabPanel("O pliku ",tableOutput("tabela1")),tabPanel("Dane",tableOutput("tabelad")))}
  })
})