r - error before pushing actionButton? -

i following error before pushing action button:

everything works expect after pushing run analysis! missing?

## app.r ## library(shiny) library(shinydashboard) library(dplyr) library(arm) library(texreg)  header <- dashboardheader()  sidebar <- dashboardsidebar(column(3, actionbutton(inputid = "go", label = "run analysis!")))  body <- dashboardbody(fluidpage(fluidrow(   box(     title = "regression table",     status = "primary",     solidheader = true,     width = 6,     uioutput("mybayesglm")   ) )))    ui <- dashboardpage(header, sidebar, body)  server <- function(input, output) {    results <- reactivevalues()    observeevent(input$go, {     # gen fake data     n<-1000     df1 <- data.frame(v1=sample(c(0,1),n,replace = t),                       v2=sample(c(0,1),n,replace = t),                       treatment=sample(c("a", "b", "c"), n, replace = t),                       noise=rnorm(n)) %>%        mutate(y=0.5*v1-0.7*v2+2*i(treatment=="b")+3*i(treatment=="c")+noise)     # run regression     mybayesglm <- bayesglm(data = df1, formula = y~treatment+v1+v2)     #ouput results in reactive list     results[[as.character(length(names(results)) + 1)]] <- mybayesglm     return(results)   }) #<-end observeevent    output$mybayesglm <- renderui({     html(       htmlreg(reactivevaluestolist(results), ci.force = true, ci.force.level = .95, caption = "")     )   })   }  shinyapp(ui, server) 

this trick:

## app.r ## library(shiny) library(shinydashboard) library(dplyr) library(arm) library(texreg)  header <- dashboardheader()  sidebar <- dashboardsidebar(column(3, actionbutton(inputid = "go", label = "run analysis!")))  body <- dashboardbody(fluidpage(fluidrow(   box(     title = "regression table",     status = "primary",     solidheader = true,     width = 6,     uioutput("mybayesglm")   ) )))    ui <- dashboardpage(header, sidebar, body)  server <- function(input, output) {    results <- reactivevalues()    observeevent(input$go, {     # gen fake data     n<-1000     df1 <- data.frame(v1=sample(c(0,1),n,replace = t),                       v2=sample(c(0,1),n,replace = t),                       treatment=sample(c("a", "b", "c"), n, replace = t),                       noise=rnorm(n)) %>%        mutate(y=0.5*v1-0.7*v2+2*i(treatment=="b")+3*i(treatment=="c")+noise)     # run regression     mybayesglm <- bayesglm(data = df1, formula = y~treatment+v1+v2)     #ouput results in reactive list     results[[as.character(length(names(results)) + 1)]] <- mybayesglm     return(results)   }) #<-end observeevent    output$mybayesglm <- renderui({     if(input$go==0)       return()     else     html(       htmlreg(reactivevaluestolist(results), ci.force = true, ci.force.level = .95, caption = "")     )   }) }  shinyapp(ui, server)