trie: better error-handling ethereum#23657 (XinFinOrg#1073)

Author: gzliudan

trie/trie.go

@@ -166,6 +166,10 @@ func (t *Trie) TryGetNode(path []byte) ([]byte, int, error) {
 }
 
 func (t *Trie) tryGetNode(origNode node, path []byte, pos int) (item []byte, newnode node, resolved int, err error) {
+	// If non-existent path requested, abort
+	if origNode == nil {
+		return nil, nil, 0, nil
+	}
 	// If we reached the requested path, return the current node
 	if pos >= len(path) {
 		// Although we most probably have the original node expanded, encoding
@@ -185,10 +189,6 @@ func (t *Trie) tryGetNode(origNode node, path []byte, pos int) (item []byte, new
 	}
 	// Path still needs to be traversed, descend into children
 	switch n := (origNode).(type) {
-	case nil:
-		// Non-existent path requested, abort
-		return nil, nil, 0, nil
-
 	case valueNode:
 		// Path prematurely ended, abort
 		return nil, nil, 0, nil