Use or operator instead of if self.set else

Co-authored-by: sourcery-ai[bot] <58596630+sourcery-ai[bot]@users.noreply.github.com>

ufpy/algebra/sets.py

@@ -47,7 +47,7 @@ def __update__(self):
 
     # Convert to other types
     def __repr__(self) -> str:
-        return f'u{self.set if self.set else '{}'}'
+        return f'u{self.set or '{}'}'
 
     def __str__(self) -> str:
         return repr(self.set) if self.set else '{}'