:around advice is passed the original function as well as all
arguments passed when calling the function.  This means that if
‘kill-all-local-variables’ is called with an argument, an advice
:around it will be called with two arguments.  Unfortunately,
‘adob--kill-all-local-variables-advice’ was not prepared to take
that optional argument which resulted in the following error:

    apply: Wrong number of arguments: #<subr adob--kill-all-local-variables-advice>, 2

Fix by properly handling the optional argument.

Fixes: #32