Use the new best_hash instead of parent_hash when calling intermediate_roots()

Using `parent_hash` is wrong because we need to call the api on top of
the newly created best block to get the intermediate roots for this
just executed block.

Author: liuchengxu

cumulus/client/cirrus-executor/src/merkle_tree.rs

@@ -48,12 +48,13 @@ pub(super) fn construct_trace_merkle_tree(
 	let mut roots = roots;
 
 	let roots_len = roots.len();
+	// roots contains at least [storage_root_after_initializing_block, state_root].
 	assert!(roots_len >= 2, "Execution trace should at least contain 2 storage roots");
 
 	let ideal_len = merkletree::merkle::next_pow2(roots_len);
 
 	if ideal_len > roots_len {
-		// The last element of trace is state_root.
+		// Fill in a full tree by replicating the last element.
 		if let Some(state_root) = roots.last().copied() {
 			roots.resize(ideal_len, state_root);
 		}

cumulus/client/cirrus-executor/src/processor.rs

@@ -194,13 +194,7 @@ where
 		(&*self.client).import_block(block_import_params, Default::default()).await?;
 
 		let mut roots =
-			self.client.runtime_api().intermediate_roots(&BlockId::Hash(parent_hash))?;
-
-		if roots.is_empty() {
-			panic!(
-				"FIXME: runtime intermediate_roots is empty, uncovered by running the sync node, related: https://github.com/paritytech/substrate/pull/8953"
-			);
-		}
+			self.client.runtime_api().intermediate_roots(&BlockId::Hash(header_hash))?;
 
 		let state_root = state_root
 			.encode()