Fixed a php notice in aps_plugin.inc.php

Author: tbrehm

server/plugins-available/aps_plugin.inc.php

@@ -28,7 +28,7 @@
 EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
-if(defined(ISPC_ROOT_PATH)) include_once(ISPC_ROOT_PATH.'/lib/classes/aps_installer.inc.php');
+if(defined('ISPC_ROOT_PATH')) include_once(ISPC_ROOT_PATH.'/lib/classes/aps_installer.inc.php');
 //require_once(ISPC_ROOT_PATH.'/lib/classes/class.installer.php');
 
 class aps_plugin