fix: nullish reference in getNodeError (#2769)

* Fix null pointer exception in getNodeError check for ExecutionRevertedError

* Update khaki-onions-teach.md

---------

Co-authored-by: Nguyen Anh Tu <tunguyen.bhtech@gmail.com>
Co-authored-by: jxom <j@wevm.dev>

.changeset/khaki-onions-teach.md

@@ -0,0 +1,5 @@
+---
+"viem": patch
+---
+
+Fixed undefined reference in `getNodeError`.

src/utils/errors/getNodeError.test.ts

@@ -297,6 +297,23 @@ test('ExecutionRevertedError', () => {
   `)
 })
 
+test('UnknownNodeError check with null cause in error chain', () => {
+  const error = new TransactionRejectedRpcError(
+    new Error('null cause', { cause: null }),
+  )
+  const result = getNodeError(error, {
+    account: address.vitalik,
+    maxFeePerGas: parseGwei('10'),
+    maxPriorityFeePerGas: parseGwei('11'),
+  })
+  expect(result).toMatchInlineSnapshot(`
+    [UnknownNodeError: An error occurred while executing: Transaction creation failed.
+
+    Details: null cause
+    Version: viem@x.y.z]
+  `)
+})
+
 test('Unknown node error', () => {
   const error = new TransactionRejectedRpcError(
     new RpcRequestError({

src/utils/errors/getNodeError.ts

@@ -68,7 +68,7 @@ export function getNodeError(
   const executionRevertedError =
     err instanceof BaseError
       ? err.walk(
-          (e) => (e as { code: number }).code === ExecutionRevertedError.code,
+          (e) => (e as { code: number } | null | undefined)?.code === ExecutionRevertedError.code,
         )
       : err
   if (executionRevertedError instanceof BaseError)