An infinite loop in include/handlers.inc can cause denial of service

An infinite loop in views/include/handlers.inc (824-826) can cause denial of service under some conditions involving broken/bad views from third party modules.

The infinite loop occurs when views_get_table_join returns null, which may be caught during development, with the developer module enabled. This is caused by bad, broken or misconfigured third party modules.

When whatchdog dblog and or syslog modules are enabled this causes a flood of watchdog notices, which can quickly eat all of the disk space available, leading to denial of service.

I propose to solve the infinite loop issue, as we can't know how views_get_table_join is used in the wild.

    while (!empty($r_join) && $r_join->left_table != $base_table) {
      $r_join = views_get_table_join($r_join->left_table, $base_table);
    }