title: Append to YCM dictionary in Vim
body: <p>I'm trying to append an entry to the dictionary <code>g:ycm_filetype_blacklist</code>. I would like to disable YouCompleteMe for Tex files, so I try adding the following line at the end of my vimrc:</p>
  
  <pre><code>let g:ycm_filetype_blacklist.tex = 1
  </code></pre>
  
  <p>At startup, Vim will complaint that the variable is not defined, but it is available afterwards, and it contains the expected default entries.</p>
  
  <p>I'm using Vim 8.0.</p>
  
  <p>How can I append an entry to this dictionary on startup without defining it from scratch?</p>