@@ -235,9 +235,11 @@ class Preferences(object):
235235 if user_setting_name in self.key_value_settings:
236236 self.key_value_settings[user_setting_name].parse(user_setting)
237237 elif user_setting_name == 'disabled_engines':
238− self.engines.parse_cookie([input_data['disabled_engines'], input_data['enabled_engines']])
238+ self.engines.parse_cookie((input_data.get('disabled_engines', ''),
239+ input_data.get('enabled_engines', '')))
239240 elif user_setting_name == 'disabled_plugins':
240− self.plugins.parse_cookie([input_data['disabled_plugins'], input_data['enabled_plugins']])
241+ self.plugins.parse_cookie((input_data.get('disabled_plugins', ''),
242+ input_data.get('enabled_plugins', '')))
241243
242244 def parse_form(self, input_data):
243245 disabled_engines = []