DT tables with language option do not render

[olivierISCIII]

For some reason, DT tables are not rendered when the language option was specified.
Note that the table is rendered when no page layout is specified.
Here is a reproducible example:

---
title: "issue flexdashboard"
output: 
  flexdashboard::flex_dashboard:
    orientation: columns
    vertical_layout: fill
---

Page 1
=====================================  

other attached packages:
[1] DT_0.33             flexdashboard_0.6.2


### Tabla
```{r}
require(DT)
datatable(iris,options = list(language = list(url = 'https://cdn.datatables.net/plug-ins/2.0.2/i18n/es-ES.json'))) 
```