Author: Zig Tan
MDL-61397 blocks: Fix null_provider namespace for blocks
Also added null provider for block_messages
http://git.moodle.org/gw?p=moodle.git;a=commit;h=d2bc47577b2555540df650cc72d23ab4639d878d
http://github.com/moodle/moodle/commit/d2bc47577b2555540df650cc72d23ab4639d878d
+ 3.3 en [privacy:metadata,block_messages]