- Fixed "PHP Notice: Undefined property:...

- Fixed "PHP Notice:  Undefined property: installer::$ispconfig_interface_installed in /tmp/trunk/install/update.php on line 337" when updating an ISPConfig server with nginx.

install/lib/installer_base.lib.php

@@ -137,7 +137,7 @@ class installer_base {
 		if(is_installed('vzctl')) $conf['openvz']['installed'] = true;
 		if(is_dir("/etc/Bastille")) $conf['bastille']['installed'] = true;
 		
-		if ($conf['services']['web'] && $conf['apache']['installed'] && is_file($conf['apache']["vhost_conf_enabled_dir"]."/000-ispconfig.vhost")) $this->ispconfig_interface_installed = true;
+		if ($conf['services']['web'] && (($conf['apache']['installed'] && is_file($conf['apache']["vhost_conf_enabled_dir"]."/000-ispconfig.vhost")) || ($conf['nginx']['installed'] && is_file($conf['nginx']["vhost_conf_enabled_dir"]."/000-ispconfig.vhost")))) $this->ispconfig_interface_installed = true;
 	}
 
 	/** Create the database for ISPConfig */