Don't handle nulls in DTO

[cecilia-donnelly]

From my conversation a couple days ago with @slifty, lightly edited:

The null patch [see 81efbe0 and b8d01da] I'm worried might be avoiding an issue and doing something we shouldn't be doing. Basically "null" is a valid value for a lot of these fields, according to HUD, and even if it isn't, the DTO traditionally isn't the place for that kind of logic; the manager is.

Dan might already be on this, but we need to handle #52 a different way.