message: Return true if chain rolled back and checkpoint not found
diff: @@ -208,8 +208,12 @@ bool CheckSyncCheckpoint(const uint256 hashBlock, const int nHeight, const CBloc
  const CBlockIndex* pindexSync;
  {
  LOCK2(cs_main, cs_hashSyncCheckpoint);
  - // sync-checkpoint should always be accepted block
  - assert(::BlockIndex().count(hashSyncCheckpoint));
  + // sync-checkpoint should always be accepted block, if not top
  + // of chain might have been rolled back due to abrupt shutdown.
  + // Return true while blocks resync.
  + if (!::BlockIndex().count(hashSyncCheckpoint)) {
  + return true;
  + }
  pindexSync = ::BlockIndex()[hashSyncCheckpoint];
  }
  