Strange error



Hi,

I posted this also as a bug but I suspect it might be just me not 
understanding the
concepts of maxima. So I am reposting it here.

The following maxima code

alphas=[];
alpha(n):=assoc(n,alphas);
alpha(5);

gives the error
========================================================
Maxima encountered a Lisp error:

Error in PROGN [or a callee]: Caught fatal error [memory may be damaged]

Automatically continuing.
========================================================
On the other hand

assoc(5,[]);

returns false (as it should).
====================================================
This is the banner of maxima

Maxima 5.9.3 http://maxima.sourceforge.net
Using Lisp GNU Common Lisp (GCL) GCL 2.6.7 (aka GCL)

Any hints?
Michel