Don't fallback to last page if $totalPages < 1.

See #693 for context. That should at least
avoid SQL errors.

Signed-off-by: Thomas Hochstein <thh@inter.net>

include/functions_entries.inc.php

@@ -412,7 +412,7 @@ function &serendipity_fetchEntries($range = null, $full = true, $limit = '', $fe
 
             // Do not allow requesting a page that doesn't exist
             // and do a fallback to the highest page number available
-            if ($serendipity['GET']['page'] > $totalPages) {
+            if ($totalPages > 0 && $serendipity['GET']['page'] > $totalPages) {
                 $serendipity['GET']['page'] = $totalPages;
             }