Fix crash when switching to a profile that cannot be opened

chrome/browser/profiles/profile_io_data.cc

Index: chrome/browser/profiles/profile_io_data.cc
diff --git a/chrome/browser/profiles/profile_io_data.cc b/chrome/browser/profiles/profile_io_data.cc
index 528be3c7316f4642a236d7df2db954af8ed9ff76..f2f5b5c2068051b704c366664642b923c15fad9d 100644
--- a/chrome/browser/profiles/profile_io_data.cc
+++ b/chrome/browser/profiles/profile_io_data.cc
@@ -1308,8 +1308,10 @@ void ProfileIOData::DestroyResourceContext() {
   // notifications by severing the link between it and the
   // cert_transparency_verifier_ and unregistering it from new STH
   // notifications.
-  cert_transparency_verifier_->SetObserver(nullptr);
-  ct_tree_tracker_unregistration_.Run();
+  if (cert_transparency_verifier_)

[Peter Kasting, 2016/06/16 07:02:11]

When can these be null?  Unless it's super obvious to the observer, consider
adding a comment about it.

+    cert_transparency_verifier_->SetObserver(nullptr);
+  if (!ct_tree_tracker_unregistration_.is_null())
+    ct_tree_tracker_unregistration_.Run();
 }
 
 std::unique_ptr<net::HttpNetworkSession>