only divide by mean whenever it's not zero

Author: basnijholt

adaptive/learner/average_learner.py

@@ -119,7 +119,9 @@ def loss(self, real=True, *, n=None):
             return np.inf
         standard_error = self.std / sqrt(n)
         aloss = standard_error / self.atol
-        rloss = standard_error / abs(self.mean) / self.rtol
+        rloss = standard_error / self.rtol
+        if self.mean != 0:
+            rloss /= abs(self.mean)
         return max(aloss, rloss)
 
     def _loss_improvement(self, n):