Fix nullptr deference in FidoRequestHandlerBase

Bug: 870193
Change-Id: Ie7131514e1cf45f958dca11df8a142ea92440cad
Reviewed-on: https://chromium-review.googlesource.com/1159992Reviewed-by: Kim Paulhamus <kpaulhamus@chromium.org>
Commit-Queue: Jun Choi <hongjunchoi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580276}

device/fido/fido_request_handler_base.cc

@@ -140,11 +140,11 @@ void FidoRequestHandlerBase::AddAuthenticator(
   active_authenticators_.emplace(authenticator->GetId(),
                                  std::move(authenticator));
 
-  if (!ShouldDeferRequestDispatchToUi(*authenticator.get()))
+  if (!ShouldDeferRequestDispatchToUi(*authenticator_ptr))
     DispatchRequest(authenticator_ptr);
 
   if (observer_)
-    observer_->FidoAuthenticatorAdded(*authenticator);
+    observer_->FidoAuthenticatorAdded(*authenticator_ptr);
 }
 
 }  // namespace device