Show better error message for unknown downtimes

refs #8902

modules/monitoring/application/controllers/DowntimeController.php

@@ -76,12 +76,14 @@ class Monitoring_DowntimeController extends Controller
     
     public function showAction()
     {
+        if (false === $this->downtime) {
+            return;
+        }
         $this->view->downtime = $this->downtime;
         $this->view->isService = $this->isService;
         $this->view->stateName = isset($this->downtime->service_description) ? 
                 Service::getStateText($this->downtime->service_state) :
                 Host::getStateText($this->downtime->host_state);
-        
         $this->view->delDowntimeForm = $this->createDelDowntimeForm();
         $this->view->listAllLink = Url::fromPath('monitoring/list/downtimes');
         $this->view->showHostLink = Url::fromPath('monitoring/host/show')

modules/monitoring/application/views/scripts/downtime/show.phtml

@@ -1,4 +1,10 @@
 <div class="controls">
+  <?php if (! isset($downtime)): ?>
+    <?= $this->translate('No scheduled downtime matching the filter.') ?>
+    </div>
+    <?php return; ?>
+  <?php endif; ?>
+   
   <?php if (! $this->compact): ?>
     <?= $this->tabs; ?>
   <?php endif ?>

modules/monitoring/application/views/scripts/list/downtimes.phtml

@@ -15,7 +15,8 @@ if (! $this->compact): ?>
 <?php
 
 if (count($downtimes) === 0) {
-    echo $this->translate('No downtimes found matching the filter') . '</div>';
+    echo $this->translate('No downtimes found matching the filter,'
+            . ' maybe the downtime already expired.') . '</div>';
     return;
 }
 ?>