Fix "Undefined index: icon" when visiting Search Servers using MySQL

Summary:
Fix "Undefined index: icon" when visiting Search Servers using MySQL

NOTE: This patch just fixes the exception at my best but this section probably deserves more improvement to show a better default.

Closes T15155

Test Plan:
- use the default Search Server configuration (that is MySQL)
- open the page Search Servers (/config/cluster/search/)
- verify that it does not explode anymore but it displays something unuseful

Reviewers: O1 Blessed Committers, avivey

Reviewed By: O1 Blessed Committers, avivey

Subscribers: avivey, speck, tobiaswiese, Matthew, Cigaryno

Maniphest Tasks: T15155

Differential Revision: https://we.phorge.it/D25070

src/applications/config/controller/services/PhabricatorConfigClusterSearchController.php

@@ -60,8 +60,20 @@ final class PhabricatorConfigClusterSearchController
 
     foreach ($service->getHosts() as $host) {
       try {
+        // Default status icon
+        //
+        // At the moment the default status is shown also when
+        // you just use MySQL as search server. So, on MySQL it
+        // shows "Unknown" even if probably it should says "Active".
+        // If you have time, please improve the MySQL getConnectionStatus()
+        // to return something more useful than this default.
+        $default_status = array(
+          'icon'  => 'fa-question-circle',
+          'color' => 'blue',
+          'label' => pht('Unknown'),
+        );
         $status = $host->getConnectionStatus();
-        $status = idx($status_map, $status, array());
+        $status = idx($status_map, $status, $default_status);
       } catch (Exception $ex) {
         $status['icon'] = 'fa-times';
         $status['label'] = pht('Connection Error');