Explicitly test for None when saving data.
Explicitly test for None when saving data.

Some values such as zero-length strings fail to be truthy but are still
valid MIME payloads. It's fine to save these blank parts, but a 'None'
value is definitely a bug in our decoding/encoding code.

PriviPK/privipk-sync-engine,nylas/sync-engine,ErinCall/sync-engine,wakermahmud/sync-engine,jobscore/sync-engine,rmasters/inbox,rmasters/inbox,wakermahmud/sync-engine,Eagles2F/sync-engine,gale320/sync-engine,nylas/sync-engine,ErinCall/sync-engine,closeio/nylas,PriviPK/privipk-sync-engine,nylas/sync-engine,wakermahmud/sync-engine,gale320/sync-engine,ErinCall/sync-engine,EthanBlackburn/sync-engine,closeio/nylas,Eagles2F/sync-engine,closeio/nylas,jobscore/sync-engine,ErinCall/sync-engine,PriviPK/privipk-sync-engine,EthanBlackburn/sync-engine,jobscore/sync-engine,rmasters/inbox,gale320/sync-engine,gale320/sync-engine,Eagles2F/sync-engine,closeio/nylas,EthanBlackburn/sync-engine,wakermahmud/sync-engine,EthanBlackburn/sync-engine,Eagles2F/sync-engine,wakermahmud/sync-engine,nylas/sync-engine,EthanBlackburn/sync-engine,ErinCall/sync-engine,rmasters/inbox,PriviPK/privipk-sync-engine,PriviPK/privipk-sync-engine,jobscore/sync-engine,Eagles2F/sync-engine,gale320/sync-engine