Fix a potential CFRelease(NULL).

It would happen if CreateClientCertificateChain() returns NULL.
Found by the clang static analyzer. Probably doesn't happen in
practice.

BUG=none
TEST=none


Review URL: http://codereview.chromium.org/8308009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@107041 0039d316-1c4b-4281-b951-d872f2087c98

net/socket/ssl_client_socket_nss.cc

@@ -2383,8 +2383,11 @@ SECStatus SSLClientSocketNSS::PlatformClientAuthHandler(
         }
       }
       if (os_error == noErr) {
-        int cert_count = CFArrayGetCount(chain);
-        CFRelease(chain);
+        int cert_count = 0;
+        if (chain) {
+          cert_count = CFArrayGetCount(chain);
+          CFRelease(chain);
+        }
         that->net_log_.AddEvent(NetLog::TYPE_SSL_CLIENT_CERT_PROVIDED,
             make_scoped_refptr(new NetLogIntegerParameter("cert_count",
                                                           cert_count)));