fix(OrderedListWalker): Support empty tries

.gitignore

@@ -6,3 +6,6 @@ target/
 
 # Environment Variables
 .env
+
+# IntelliJ IDE
+.idea

crates/mpt/src/list_walker.rs

@@ -117,6 +117,9 @@ where
                     node => Ok(Self::fetch_leaves(node, fetcher)?),
                 }
             }
+            TrieNode::Empty => {
+                Ok(Default::default())
+            }
             _ => anyhow::bail!("Invalid trie node type encountered"),
         }
     }
@@ -156,6 +159,7 @@ where
 mod test {
     use super::*;
     use crate::{
+        NoopTrieDBFetcher,
         ordered_trie_with_encoder,
         test_util::{
             get_live_derivable_receipts_list, get_live_derivable_transactions_list,
@@ -221,4 +225,13 @@ mod test {
             VALUES
         );
     }
+
+    #[test]
+    fn test_empty_list_walker() {
+        assert!(
+            OrderedListWalker::fetch_leaves(&TrieNode::Empty, &NoopTrieDBFetcher)
+                .expect("Failed to traverse empty trie")
+                .is_empty()
+        );
+    }
 }