Bad schema definition fails in MySQL Strict mode

As described here: http://www.palantir.net/blog/beware-mysql-51-my-son

Viewreference defines its vid field as NOT NULL default 0. CCK then uses actual NULL values when a viewreference is not used. MySQL 5.1 for many versions accidentally forces strict mode handling of NULL fields. Hilarity ensues as viewreference fields now become mandatory as not specifying them causes an SQL error.

The solution is to allow NULL values in that column and adjust other code accordingly.