A tiny bug in zeromatrix

I found that zeromatrix (n,m) gives somewhat confusing for
incorrect values of n,m:

  (%i1) zeromatrix (n,m);

  Incorrect argument to `ematrix':
  [n, m, 1, 1]
   -- an error.  To debug this try debugmode(true);

  (%i2) zeromatrix (-4,4);

  Incorrect argument to `ematrix':
  [- 4, 4, 1, 1]
   -- an error.  To debug this try debugmode(true);

Maybe it's better to give a more clear error message
(or a noun form in some cases?).

Now zeromatrix is just defined by

  (defmfun $zeromatrix (m n) ($ematrix m n 0 1 1))

in src/csimp2.lisp.

-- 
Pungenday, Bureaucracy 54, 3174 YOLD
Alexey Beshenov http://beshenov.ru/