title: Shiny splitLayout and selectInput issue
body: <p>When I combine the splitLayout and selectInput in R Shiny, there is something wrong.</p>
  
  <p>The dropdown list of choices cannot be displayed properly. </p>
  
  <p>How can we address this issue.</p>
  
  <p>Please check the reproducible code.</p>
  
  <pre><code>library(shiny)
  
  server &lt;- function(input, session, output) {
  
    output$select_1 = renderUI({
      selectInput("select_input","select", choices = LETTERS)
    })
  
  
  
  }
  
  ui &lt;- fluidPage(
    splitLayout(
      uiOutput("select_1")
    )
  )
  
  shinyApp(ui = ui, server = server)
  </code></pre>
  
  <p>I have 8 selectInputs that I want to place evenly side by side in one row. </p>
  
  <p>Using fluidrow is not OK because the column width can only be integers. </p>
  
  <p>I wonder if there is any alternative way to do this.</p>