Erreur avec l'app shiny

Sur la page Web:
```
An error has occurred. Check your logs or contact the app author for clarification.
```

Dans les logs `/var/log/shiny-server/`
```
Warning: Error in <Anonymous>: cannot open file 'Rplots.pdf'
  102: <Anonymous>
Warning: Error in <Anonymous>: cannot open file 'Rplots.pdf'
  102: <Anonymous>
```
