There are three bugs here:
- we should check if the value type is transformable instead of being
compatible, since that's all we care about in order to call
g_value_transform()
- the check is only meaningful in the direction
passed-in-type->column-type and not viceversa
- we should init the destination GValue to the column type before
calling g_value_transform on it, or the destination type information
will be missing and the method will fail
Thanks to Jasper St. Pierre and Colin Walters for all the help in
tracking this down.