Catch UnpackValueError when loading the Gmail metadata cache
Catch UnpackValueError when loading the Gmail metadata cache

Summary: Fixes T199.

Test Plan: Tested by launching a sync, stopping it midway and manually corrupting the cache.

Reviewers: spang

Reviewed By: spang

Maniphest Tasks: T199

Differential Revision: https://review.inboxapp.com/D289

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