Merge pull request #1164 from mathics/fixiszero

fix rational is_zero

Author: mmatera

mathics/core/expression.py

@@ -2137,7 +2137,7 @@ def __neg__(self) -> 'Rational':
 
     @property
     def is_zero(self) -> bool:
-        return self.numerator().is_zero and not self.denominator().is_zero()
+        return self.numerator().is_zero # (implicit) and not (self.denominator().is_zero)
 
 
 class Real(Number):