title: I get an error in User Interface when i use select input
body: <p>i am using the following code in my UI</p>
  <pre><code>  selectInput(&quot;param&quot;, 
                &quot;Parameter:&quot;,
                label = c(&quot;S Blood Pressure&quot;, &quot;D Blood Pressure&quot;),
                choices = c(&quot;SBP&quot;, &quot;DBP&quot;)
  </code></pre>
  <p>i get the following error on my UI page when i run UI.r script.</p>
  <p>An error has occurred!
  Text to be written must be a length-one character vector</p>