RE: Wrong type argument: arrayp, nil

[Drew Adams]

First, do this, to get a human-readable backtrace:

1. Set variable `debug-on-error' to t.
2. Provoke the error, so you can see which function is problematic.
   Quit the debugger using `q'.
3. Load the source files for the package in question.  This is to
   give you a more human-readable backtrace.
4. Provoke the error again.

You can now report the problem to the package maintainer.  If the
responsible code is delivered as part of Emacs (not some 3rd party)
then report the problem to Emacs Dev using `M-x report-emacs-bug'.

If you want to debug it further yourself, step through the debugger
after step #4 above.  Use `d' to single-step and `c' to skip through
a step.  Use `q' to quit or step through until the problematic
function returns.

Some people prefer `edebug' to `debug'.  I prefer `debug', which is
what you get with the above recipe.