Add a "None" language as the first item in the Language menu (with a separator) that mimics "Normal Text".

    Language
==============
  None
--------------
  A         >
  B         >
  etc.
  YAML
---------------
  User defined

This will be much easier to find when the user wants to disable a language that is in action without his/her consent, because the edited file has an obscure file extension ;-)