don't return a state in state_at if the db prunes and the block is before guaranteed history

util/src/journaldb/archivedb.rs

@@ -175,6 +175,8 @@ impl JournalDB for ArchiveDB {
 	fn state(&self, id: &H256) -> Option<Bytes> {
 		self.backing.get_by_prefix(&id.bytes()[0..12]).and_then(|b| Some(b.to_vec()))
 	}
+
+	fn does_pruning(&self) -> bool { false }
 }
 
 #[cfg(test)]

util/src/journaldb/traits.rs

@@ -42,4 +42,7 @@ pub trait JournalDB : HashDB + Send + Sync {
 	fn state(&self, _id: &H256) -> Option<Bytes> {
 		None
 	}
+
+	/// Whether this database does pruning.
+	fn does_pruning(&self) -> bool { true }
 }