Fix crash when displaying a null certificate.

content/browser/devtools/protocol/security_handler.cc

Index: content/browser/devtools/protocol/security_handler.cc
diff --git a/content/browser/devtools/protocol/security_handler.cc b/content/browser/devtools/protocol/security_handler.cc
index 168bd5ec5bd7bd10c2d64b62e8ea4a22494aec8c..f3ff1405037807ebee3a516939dd5fa40abbf1bc 100644
--- a/content/browser/devtools/protocol/security_handler.cc
+++ b/content/browser/devtools/protocol/security_handler.cc
@@ -156,6 +156,8 @@ Response SecurityHandler::ShowCertificateViewer() {
   WebContents* web_contents = WebContents::FromRenderFrameHost(host_);
   scoped_refptr<net::X509Certificate> certificate = web_contents->
       GetController().GetLastCommittedEntry()->GetSSL().certificate;
+  if (!certificate)
+    return Response::InternalError("Could not find certificate");
   web_contents->GetDelegate()->ShowCertificateViewerInDevTools(
       web_contents, certificate);
   return Response::OK();