Simplify return statement in parent_directory for better readability

Signed-off-by: Aayush Kumar <aayush214.kumar@gmail.com>

Author: aayushkdev

scanpipe/models.py

@@ -2889,7 +2889,7 @@ def get_path_segments_with_subpath(self):
     def parent_directory(self):
         """Return the parent path for this CodebaseResource or None."""
         parent_path = parent_directory(str(self.path), with_trail=False)
-        return None if parent_path == "" else parent_path
+        return parent_path or None
 
     def has_parent(self):
         """