If an item is deleted, fetching the first subject on its event would
return the wrong this because it only traversed to the end of the chain.
For the moment, fix this by ensuring that whatever's at the end of
the chain has an entity type (or return null).
Ensure link node have some identifiable characteristics
Log more debug when a serialization barfs
Log more debug when a serialization fails
Ruby script to add debug to link nodes
Additional sanity check on ActionManager