Better error handling for non-IdP domains

scripts/check_primary_support

@@ -23,8 +23,10 @@ if (process.argv.length !== 3) {
 var domain = process.argv[2];
 
 primary.checkSupport(domain, function(err, urls, publicKey) {
-  if (err) {
-    process.stderr.write("error: " + err + "\n");
+  if (err || publicKey === null) {
+    if (err) {
+      process.stderr.write("error: " + err + "\n");
+    }
     process.exit(1);
   }
   console.log('Priary domain: ', domain);