I have found a couple of Scrubber issues in 2.1.9 which I have patched on the Release_2_1-maint branch.
These issues involved a message with a message/delivery-status part which parses into text/plain sub-parts with None payloads, and a message with an improperly RFC 2047 encoded filename which had a trailing null byte.
In looking at how the Release_2_1-maint patches port to the Trunk, I've seen some other problems.
I have developed the attached Scrubber.patch.txt patch for the Trunk which I think fixes the problems I saw in 2.1.9 and fixes the other problems I see.
I would appreciate others, particularly Tokio, looking at this to see if it seems correct.