contractcourt: catch error when no historical bucket exists

For older nodes, this bucket was never created, so we'll get an error if
we try and query it. In this commit, we catch this error like we do when
a given channel doesn't have the information (but the bucket actually
exists).

Fixes #6155

contractcourt/channel_arbitrator.go

@@ -618,6 +618,8 @@ func (c *ChannelArbitrator) relaunchResolvers(commitSet *CommitSet,
 	// If we don't find this channel, then it may be the case that it
 	// was closed before we started to retain the final state
 	// information for open channels.
+	case err == channeldb.ErrNoHistoricalBucket:
+		fallthrough
 	case err == channeldb.ErrChannelNotFound:
 		log.Warnf("ChannelArbitrator(%v): unable to fetch historical "+
 			"state", c.cfg.ChanPoint)
@@ -1947,6 +1949,8 @@ func (c *ChannelArbitrator) prepContractResolutions(
 	// If we don't find this channel, then it may be the case that it
 	// was closed before we started to retain the final state
 	// information for open channels.
+	case err == channeldb.ErrNoHistoricalBucket:
+		fallthrough
 	case err == channeldb.ErrChannelNotFound:
 		log.Warnf("ChannelArbitrator(%v): unable to fetch historical "+
 			"state", c.cfg.ChanPoint)