Incorrect postal code not handled correctly

[JohanBraeken]

When signing up with a postcode that is not an integer, the registration "completes", but also a "500 Internal server error" is thrown.
The user doesn't receive any indication of what went wrong.

On the server side, the following is logged:

/site-packages/sqlalchemy/engine/default.py:436: Warning: Incorrect integer value: 'B-1234' for column 'postalcode' at row 1
cursor.execute(statement, parameters)
[25/Aug/2014 16:00:31] "POST /register HTTP/1.1" 500 -

In the database, the postal code for that user has become '0', effectively corrupting the user input.

If the registration fails for any reason, no data should be changed/added in the database.
Postal codes are also not integers, especially not in other countries than Belgium.