Re-added numpy raise divide catch.

gprMax/fractals.py

@@ -17,6 +17,7 @@
 # along with gprMax.  If not, see <http://www.gnu.org/licenses/>.
 
 import numpy as np
+np.seterr(divide='raise')
 
 from gprMax.constants import floattype, complextype
 from gprMax.utilities import round_value