[Presentation API] check if frame() is null before accessing presentation.receiver attr

third_party/WebKit/Source/modules/presentation/Presentation.cpp

Index: third_party/WebKit/Source/modules/presentation/Presentation.cpp
diff --git a/third_party/WebKit/Source/modules/presentation/Presentation.cpp b/third_party/WebKit/Source/modules/presentation/Presentation.cpp
index 6d38d46fd71a7daf4d619eb8b04f2cb361d8330f..aa15f73e031d3796661a692a3ff9141cf974984c 100644
--- a/third_party/WebKit/Source/modules/presentation/Presentation.cpp
+++ b/third_party/WebKit/Source/modules/presentation/Presentation.cpp
@@ -48,13 +48,16 @@ void Presentation::setDefaultRequest(PresentationRequest* request) {
 }
 
 PresentationReceiver* Presentation::receiver() {
-  PresentationController* controller = PresentationController::from(*frame());
-  auto* client = controller ? controller->client() : nullptr;
+  if (!frame())
+    return nullptr;
   // TODO(crbug.com/647296): only return something if the Blink instance is
   // running in presentation receiver mode. The flag PresentationReceiver could
   // be used for that.
-  if (!m_receiver)
+  if (!m_receiver) {
+    PresentationController* controller = PresentationController::from(*frame());
+    auto* client = controller ? controller->client() : nullptr;
     m_receiver = new PresentationReceiver(frame(), client);
+  }
   return m_receiver;
 }