Check the currently stable exists
@@ -1026,7 +1026,7 @@ class Project(models.Model):
# return immediately if the current stable is managed by the user and
# not automatically by Read the Docs (``machine=False``)
current_stable = self.get_stable_version()
- if not current_stable.machine:
+ if current_stable and not current_stable.machine:
return None
versions = self.versions(manager=INTERNAL).all()
