Fixed error when user doesn't have birthdate

Author: Seluj78

backend/PyMatcha/models/user.py

@@ -193,10 +193,13 @@ def to_dict(self) -> Dict:
         returned_dict.pop("password")
         returned_dict.pop("previous_reset_token")
 
-        today = datetime.datetime.utcnow()
-        returned_dict["age"] = (
-            today.year - self.birthdate.year - ((today.month, today.day) < (self.birthdate.month, self.birthdate.day))
-        )
+        if self.birthdate:
+            today = datetime.datetime.utcnow()
+            returned_dict["age"] = (
+                today.year
+                - self.birthdate.year
+                - ((today.month, today.day) < (self.birthdate.month, self.birthdate.day))
+            )
         return returned_dict
 
     @classmethod