fixed serialization in case of null values read

src/server/BreCal/schemas/model.py

@@ -45,16 +45,27 @@ class EvaluationType(IntEnum):
     yellow = 2
     red = 3
 
+    @classmethod
+    def _missing_(cls, value):
+        return cls.undefined
+
 class NotificationType(IntEnum):
     undefined = 0
     email = 1
     push = 2
+    @classmethod
+    def _missing_(cls, value):
+        return cls.undefined
 
 class ShipcallType(IntEnum):
     undefined = 0
     arrival = 1
     departure = 2
     shifting = 3
+    
+    @classmethod
+    def _missing_(cls, value):
+        return cls.undefined
 
 
 @dataclass