Improve error message printed in SEV

Summary:
D3542 caused a SEV for us.
Make it better for future.

Test Plan: SEV

Reviewers: btrahan, epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D3614

src/aphront/configuration/AphrontApplicationConfiguration.php

@@ -140,7 +140,7 @@ abstract class AphrontApplicationConfiguration {
       $blogs = id(new PhameBlogQuery())->withDomain($host)->execute();
       $blog = reset($blogs);
       if (!$blog) {
-        if ($prod_uri) {
+        if ($prod_uri && $prod_uri != $base_uri) {
           $prod_str = ' or '.$prod_uri;
         } else {
           $prod_str = '';