stream: treat null asyncIterator as undefined

According to the spec, getIterator should normalize incoming method to
undefined if it is either undefined or null. This PR enforces that spec
compliance with passed WPT.

PR-URL: #55119
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Matthew Aitken <maitken033380023@gmail.com>
Reviewed-By: Mattias Buelens <mattias@buelens.com>

lib/internal/webstreams/util.js

@@ -230,11 +230,12 @@ function createAsyncFromSyncIterator(syncIteratorRecord) {
   return { iterator: asyncIterator, nextMethod, done: false };
 }
 
+// Refs: https://tc39.es/ecma262/#sec-getiterator
 function getIterator(obj, kind = 'sync', method) {
   if (method === undefined) {
     if (kind === 'async') {
       method = obj[SymbolAsyncIterator];
-      if (method === undefined) {
+      if (method == null) {
         const syncMethod = obj[SymbolIterator];
 
         if (syncMethod === undefined) {

test/wpt/status/streams.json

@@ -16,13 +16,6 @@
   "readable-streams/cross-realm-crash.window.js": {
     "skip": "Browser-specific test"
   },
-  "readable-streams/from.any.js": {
-    "fail": {
-      "expected": [
-        "ReadableStream.from ignores a null @@asyncIterator"
-      ]
-    }
-  },
   "readable-streams/owning-type-message-port.any.js": {
     "fail": {
       "note": "Readable streams with type owning are not yet supported",