title: Content doesn't show up in the dashboard body if the sidebar menu is dynamically created
body: <p>I noticed if the sidebar menu is created dynamically by the server code, the content doesn't show up when the app loads until after a tab is clicked.</p>
  
  <p>In the example, I used the sample code from the shiny dashboard get started page. The app runs as expected. However, as you can see, I change the sidebar menu to be dynamically created, a blank page shows up when app loads. I have to click on the first tab at the side bar to bring up the page. Is there a way to display a default page, namely the dashboard tab page?  Please note I entered an issue on shiny dashboard github page.  Thanks much for your help.</p>
  
  <pre><code>`## app.R ##
  library(shinydashboard)
  
  ui &lt;- dashboardPage(
  dashboardHeader(title = "Basic dashboard"),
  ## Sidebar content
  # dashboardSidebar(
  # sidebarMenu(
  # menuItem("Dashboard", tabName = "dashboard", icon = icon("dashboard")),
  # menuItem("Widgets", tabName = "widgets", icon = icon("th"))
  # )
  # ),
  
  dashboardSidebar(width=150, sidebarMenuOutput("sideMenu")
  ),
  
  dashboardBody(
  
  tabItems(
    # First tab content
    tabItem(tabName = "dashboard",
            fluidRow(
              box(plotOutput("plot1", height = 250)),
  
              box(
                title = "Controls",
                sliderInput("slider", "Number of observations:", 1, 100, 50)
              )
            )
    ),
  
    # Second tab content
    tabItem(tabName = "widgets",
            h2("Widgets tab content")
    )
  )
  )
  )
  
  server &lt;- function(input, output, session) {
  
  output$sideMenu &lt;- renderMenu({
  sidebarMenu(
  menuItem("Dashboard", tabName = "dashboard", icon = icon("dashboard")),
  menuItem("Widgets", tabName = "widgets", icon = icon("th"))
  )
  })
  
  set.seed(122)
  histdata &lt;- rnorm(500)
  
  output$plot1 &lt;- renderPlot({
  data &lt;- histdata[seq_len(input$slider)]
  hist(data)
  })
  }
  
  shinyApp(ui, server)`
  </code></pre>