title: runApp() from shiny is not working from code or RStudio's button
body: <p>I can not run a shiny app, neither by the RStudio's button "Run App" or  directly with the code runApp()</p>
  
  <p>I've been using this shiny app for many years. But recently, without any changes, the app stop working when I press the button "Run App" in RStudio. Then I enter the command runApp() and it doesn't work neither.</p>
  
  <p>When I press the RStudio button "Run App" I get:</p>
  
  <pre><code>runApp('')
  Error in shinyAppDir(x) : No Shiny application exists at the path ""
  </code></pre>
  
  <p>When I enter the command <code>shiny::runApp()</code> at the beginning of the app, I get:</p>
  
  <pre><code>Listening on http://127.0.0.1:3642
  Warning: Error in runApp: Can't call `runApp()` from within `runApp()`. If your application code contains `runApp()`, please remove it.
    51: stop
    50: runApp
  Error in runApp() : 
    Can't call `runApp()` from within `runApp()`. If your application code contains `runApp()`, please remove it.
  </code></pre>
  
  <p>The working directory is good. </p>
  
  <p>So, I'm stuck. I can not run the app.</p>