Review @Nonnull constraint checking ?

[Tom Zeller]

Just cruising through code and saw a couple of places in
AbstractIdPSession where a @Nonnull constraint is not checked, for
example getAddressFamily() and checkAddress(). I realize the coding
conventions say "should" rather than "must" check, however, my
suggestion is to add constraint checking wherever it is missing.

It would be nice if there was a checkstyle rule or something automatic
to find these.

Pending any objections, Rod, is this something you are interested in handling ?