Rafael La Buonora

Hi! I was going through Mastering Shiny and noticed that renderTable changes "NA" to NA: ```library(shiny) ui

I worked around this problem with something based on this code: https://www.garrickadenbuie.com/blog/add-a-generated-table-of-contents-anywhere-in-rmarkdown/

Thanks man! I went through the programming assignments a while ago and want to get back into reading the book, the solutions are super useful!