Speculative fix for ChromeWebViewGuestDelegate crash.

chrome/browser/guest_view/web_view/chrome_web_view_guest_delegate.cc

Index: chrome/browser/guest_view/web_view/chrome_web_view_guest_delegate.cc
diff --git a/chrome/browser/guest_view/web_view/chrome_web_view_guest_delegate.cc b/chrome/browser/guest_view/web_view/chrome_web_view_guest_delegate.cc
index 170a56111249dc4fab8ee22858a3f9603cdbaa29..3b8fe542d34c5d51bbb4877f675afe4802e9e4c5 100644
--- a/chrome/browser/guest_view/web_view/chrome_web_view_guest_delegate.cc
+++ b/chrome/browser/guest_view/web_view/chrome_web_view_guest_delegate.cc
@@ -50,6 +50,11 @@ bool ChromeWebViewGuestDelegate::HandleContextMenu(
   DCHECK(menu_delegate);
 
   pending_menu_ = menu_delegate->BuildMenu(guest_web_contents(), params);
+  // It's possible for the returned menu to be null, so early out to avoid
+  // a crash. TODO(wjmaclean): find out why it's possible for this to happen
+  // in the first place, and if it's an error.
+  if (!pending_menu_)
+    return false;
 
   // Pass it to embedder.
   int request_id = ++pending_context_menu_request_id_;