Don't access context during OOM reporting if it's not available.

src/string-stream.cc

Index: src/string-stream.cc
diff --git a/src/string-stream.cc b/src/string-stream.cc
index 02f6f1c2bb81d4b6b710b4f16568b143488c0015..3a8ac34b3850d3c46fa292a3ac4158fc379a95be 100644
--- a/src/string-stream.cc
+++ b/src/string-stream.cc
@@ -529,7 +529,7 @@ void StringStream::PrintPrototype(JSFunction* fun, Object* receiver) {
   Isolate* isolate = fun->GetIsolate();
   if (receiver->IsNull() || receiver->IsUndefined() || receiver->IsJSProxy()) {
     print_name = true;
-  } else {
+  } else if (isolate->context() != nullptr) {
     if (!receiver->IsJSObject()) {
       receiver = receiver->GetRootMap(isolate)->prototype();
     }