use database-backed sessions in single user mode

include/sessions.php

@@ -106,13 +106,11 @@
 	}
 
 	if (\Config::get_schema_version() >= 0) {
-		if (!\Config::get(\Config::SINGLE_USER_MODE)) {
-			session_set_save_handler('\Sessions\ttrss_open',
-				'\Sessions\ttrss_close', '\Sessions\ttrss_read',
-				'\Sessions\ttrss_write', '\Sessions\ttrss_destroy',
-				'\Sessions\ttrss_gc');
-			register_shutdown_function('session_write_close');
-		}
+		session_set_save_handler('\Sessions\ttrss_open',
+			'\Sessions\ttrss_close', '\Sessions\ttrss_read',
+			'\Sessions\ttrss_write', '\Sessions\ttrss_destroy',
+			'\Sessions\ttrss_gc');
+		register_shutdown_function('session_write_close');
 
 		if (!defined('NO_SESSION_AUTOSTART')) {
 			if (isset($_COOKIE[session_name()])) {