Event types are uniqued by using the addresses of a local static defined in a header files, but it isn't the same across shared library boundaries and plugins can't currently handle ImplicitNullDerefEvents.
Please reupload with full context (-U9999).
nit: Static fields initialize to 0 without out of line definition.
Never mind, you still have to define it. It's been a while since I used static :).
I committed both patches as rC344823 but it seems that Phabricator doesn't pick up closing multiple revisions with the same commit, so closing manually.