[horde] Upgrading from horde-webmail-1.2.2 to horde-webmail-1.2.3

[Marco]

Hi,
I execute setup.php to upgrade horde-webmail-edition from 1.2.2 to 1.2.3.

I make step 4 to upgrade from previous version. I enter right username 
and password for the mysql db. I receive this error:

---------------------------------------------------------------------
Writing main configuration file
Loading database module...
Updating database...
[ ERROR! ] Reading the existing table structure failed. Error messages:
MDB2_Schema Error: schema validation error
default value of "alarm_start" is incorrect: "" is not of type "timestamp"

Running post-update scripts...
Done updating Horde Groupware Webmail Edition.
----------------------------------------------------------------------


Could you help me to know why this happens?
I don't know if I can consider upgrade successful or not.


Thank you very much for every hints you could tell me.
Best Regards
marco