fix redirects after schema upgrade; fix logout requiring valid schema

backend.php

@@ -124,7 +124,7 @@
 
 	$error = sanity_check($link);
 
-	if ($error['code'] != 0) {
+	if ($error['code'] != 0 && $op != "logout") {
 		print json_encode(array("error" => $error));
 		return;
 	}

db-updater.php

@@ -155,7 +155,8 @@ function confirmOP() {
 		print "<p>".T_sprintf("Finished. Performed <b>%d</b> update(s) up to schema
 			version <b>%d</b>.", $num_updates, $version)."</p>";
 
-		print "<form method=\"GET\" action=\"backend.php?op=logout\">
+		print "<form method=\"GET\" action=\"backend.php\">
+			<input type=\"hidden\" name=\"op\" value=\"logout\">
 			<input type=\"submit\" value=\"".__("Return to Tiny Tiny RSS")."\">
 			</form>";
 

register.php

@@ -148,7 +148,8 @@
 		if (!ENABLE_REGISTRATION) {
 			print_error(__("New user registrations are administratively disabled."));
 
-			print "<p><form method=\"GET\" action=\"backend.php?op=logout\">
+			print "<p><form method=\"GET\" action=\"backend.php\">
+				<input type=\"hidden\" name=\"op\" value=\"logout\">
 				<input type=\"submit\" value=\"".__("Return to Tiny Tiny RSS")."\">
 				</form>";
 			return;