how to ignore "Unable to compute the LU factorization"

I'm running loops over a two-variable nonlinear set of two equations
using mnewton, e.g.,
ELresults_rl:mnewton([eq_e_rl,eq_i_rl],[w_e,w_i],[e_ini,i_ini])
which is embedded in a loop over other variable values.  I.e., it is
being called many times.

This works pretty well most of the time.  However, once in awhile I get
Unable to compute the LU factorization
#0: solve_by_lu(
Maxima encountered a Lisp error:
and then I get kicked out of the loop over mnewton, not even trying all
the other values.  All hell breaks loose, and depending on the machine
and lisp version I'm using I get a string of other lisp complaints.
(I.e., I seem to get the same problems at the same values, so yes this
is some problem being fed to mnewton by the algebra in the equations
developed by my problem.)

I'd like to be able to simple ignore these cases produced by some merror
in an LU function.  E.g., the results are fed to a file that is processed
by gnuplot, so NaN's are just fine.  Is there any setting I can give to
my batch jobs to do this?

Thanks.

Lester