#5091 spectral_rep prints raw Lisp debug output when the spectrum cannot be found

[David Scherfgen]

(%i1) display2d:false$
(%i2) load(linearalgebra)$
(%i3) spectral_rep(matrix([0,0,0,0,1],[1,0,0,0,1],[0,1,0,0,0],[0,0,1,0,0],
                          [0,0,0,1,0]));

(RATVARS = ((MLIST SIMP)) GCD = '$GCD ALGEBRAIC = T)
(RATFAC = NIL) Unable to find the spectrum
 -- an error. To debug this try: debugmode(true);

Only the "Unable to find the spectrum" error should reach the user. Instead two lines of raw Lisp are printed first, with internal uppercase symbols, a dollar-sign prefix, and an empty Maxima list shown as ((MLIST SIMP)) rather than []. These cannot be switched off. The GCD field is also wrong on its own terms: it prints the literal symbol '$GCD where its neighbours print values, whereas gcd is bound to spmod at that point. matrixexp on the same matrix produces the identical output, since it goes through spectral_rep.

Detected by Claude.

[Barton Willis]

I'll fix this.