old_contents: import json
  
  from odoo import fields
  
  #
  # Definition and implementation of serialized fields: override
  #
  
  
  def convert_to_cache(self, value, record, validate=True):
      # cache format: dict / list
      if value is False:
          value = {}
      return value if isinstance(value, (dict, list)) else json.loads(value)
  
  
  fields.Serialized.convert_to_cache = convert_to_cache
  
new_contents: import json
  
  from odoo import fields
  
  #
  # Definition and implementation of serialized fields: override
  #
  
  
  def convert_to_cache(self, value, record, validate=True):
      # cache format: dict / list
      if value is False or value is None:
          value = {}
      return value if isinstance(value, (dict, list)) else json.loads(value)
  
  
  fields.Serialized.convert_to_cache = convert_to_cache
  
subject: fix for None value