Updating Associated Metadata Provider to follow the existing pattern.

cc @dougbu @rynowak 
- sounds like you've got a new opportunity for an NRE.  my thanks to @rynowak for noticing -- I'd made the mistaken assumption other changes guaranteed `includeProperties` was non-`null`.
- if all you want is to change from `includeProperties` being empty leading to `includeProperty==true` to that meaning `includeProperty=false`, just remove the old line 41.