This fixes systemtest Relax_disp.test_finite_value.
Example:
x = np.array([np.inf, -np.inf, np.nan, -128, 128])
np.nan_to_num(x)
array([ 1.79769313e+308, -1.79769313e+308, 0.00000000e+000,
-1.28000000e+002, 1.28000000e+002])
bug #22552(https://gna.org/bugs/index.php?22552): Chi2 value returned from C-code Curve-fitting return 0.0 for wrong parameters -> Expected influence on Monte-Carlo sim.
Ref: http://docs.scipy.org/doc/numpy/reference/generated/numpy.nan_to_num.html
