Fix ZeroDivisionError

When there are no fusion events at all, FuMa crashes because the progress is
calculated relative to the total number of fusion events.

This fixes issue yhoogstrate#43

fuma/ComparisonTriangle.py

@@ -147,7 +147,10 @@ def prune_duplicates(self,merged_fusions):
 
 	def log_progress(self,n_total, passed, previous_percentage):
 		# Print percentage - doesn't entirely fit yet
-		percentage = 100.0 * (float(passed) / float(n_total))
+                try:
+                    percentage = 100.0 * (float(passed) / float(n_total))
+                except ZeroDivisionError:
+                    percentage = 100.0
 		if percentage >= previous_percentage + 5.0 or passed == n_total:# Repport each 5%
 			self.logger.debug(str(round(percentage,1))+"% completed")
 			previous_percentage = percentage