Serialization issue with profile jdbc-session

[cbellone]

If a user does not select a valid ticket quantity, the system raises the following exception

org.springframework.core.serializer.support.SerializationFailedException: Failed to serialize object using DefaultSerializer; nested exception is java.io.NotSerializableException: alfio.controller.form.ReservationForm
	at org.springframework.core.serializer.support.SerializingConverter.convert(SerializingConverter.java:68)
	at org.springframework.core.serializer.support.SerializingConverter.convert(SerializingConverter.java:35)
	at org.springframework.core.convert.support.GenericConversionService$ConverterAdapter.convert(GenericConversionService.java:386)
	at org.springframework.core.convert.support.ConversionUtils.invokeConverter(ConversionUtils.java:37)