Fix an issue where 'Attending' would appear on calendar view unnecessarily

Summary:
Ref T10295

* Viewing Upcoming Events in the calendar would display 'Attending: ' even if there were not attendees. This caused confusion, such as 'Is it telling me I am "Attending?"'
* When a calendar event has no attendees, simply do not display the 'Attending: ' label

Test Plan:
* Add a new event with no one attending.
* Add a new event with one or more attendees.
* View the Upcoming Events query of the Calendar app.
* Notice how the one with no attendees does not show 'Attending: ' while the other with attendees will show the already existing 'Attending: jdoe, ssmith' label.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T10295

Differential Revision: https://secure.phabricator.com/D15207

src/applications/calendar/query/PhabricatorCalendarEventSearchEngine.php

@@ -266,7 +266,6 @@ final class PhabricatorCalendarEventSearchEngine
     $list = new PHUIObjectItemListView();
 
     foreach ($events as $event) {
-      $duration = '';
       $event_date_info = $this->getEventDateLabel($event);
       $creator_handle = $handles[$event->getUserPHID()];
       $attendees = array();
@@ -275,18 +274,6 @@ final class PhabricatorCalendarEventSearchEngine
         $attendees[] = $invitee->getInviteePHID();
       }
 
-      $attendees = pht(
-        'Attending: %s',
-        $viewer->renderHandleList($attendees)
-          ->setAsInline(1)
-          ->render());
-
-      if (strlen($event->getDuration()) > 0) {
-        $duration = pht(
-          'Duration: %s',
-          $event->getDuration());
-      }
-
       if ($event->getIsGhostEvent()) {
         $title_text = $event->getMonogram()
           .' ('
@@ -302,9 +289,25 @@ final class PhabricatorCalendarEventSearchEngine
         ->setObject($event)
         ->setHeader($title_text)
         ->setHref($event->getURI())
-        ->addAttribute($event_date_info)
-        ->addAttribute($attendees)
-        ->addIcon('none', $duration);
+        ->addAttribute($event_date_info);
+
+      if ($attendees) {
+        $attending = pht(
+          'Attending: %s',
+          $viewer->renderHandleList($attendees)
+            ->setAsInline(1)
+            ->render());
+
+        $item->addAttribute($attending);
+      }
+
+      if (strlen($event->getDuration()) > 0) {
+        $duration = pht(
+          'Duration: %s',
+          $event->getDuration());
+
+        $item->addIcon('none', $duration);
+      }
 
       $list->addItem($item);
     }