Fixed Page::expires(0) that was not getting picked up

CHANGELOG.md

@@ -10,6 +10,7 @@
 1. [](#bugfix)
     * Fixed a minor bug in Number validation [#1329](https://github.com/getgrav/grav/issues/1329)
     * Fixed exception when trying to find user account and there is no `user://accounts` folder
+    * Fixed issue when setting `Page::expires(0)` [Admin #1009](https://github.com/getgrav/grav-plugin-admin/issues/1009)
 
 # v1.1.17
 ## 02/17/2017

system/src/Grav/Common/Page/Page.php

@@ -1208,7 +1208,7 @@ class Page
             $this->expires = $var;
         }
 
-        return empty($this->expires) ? Grav::instance()['config']->get('system.pages.expires') : $this->expires;
+        return !isset($this->expires) ? Grav::instance()['config']->get('system.pages.expires') : $this->expires;
     }
 
     /**