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

channeldb/db.go

@@ -329,6 +329,7 @@ var dbTopLevelBuckets = [][]byte{
 	metaBucket,
 	closeSummaryBucket,
 	outpointBucket,
+	historicalChannelBucket,
 }
 
 // Wipe completely deletes all saved state within all used buckets within the