Update coderdojochi/models/session.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: karbassi

coderdojochi/models/session.py

@@ -272,7 +272,7 @@ def save(self, *args, **kwargs):
         if self.mentor_capacity is None:
             self.mentor_capacity = int(self.capacity / 2)
 
-        self.mentor_capacity = max(self.mentor_capacity, 0)
+        self.mentor_capacity = max(self.mentor_capacity if self.mentor_capacity is not None else 0, 0)
 
         # Capacity check
         if self.capacity is None: