Unreliable fopen call

[shennetsind]

a reported by Kas in http://hercules.ws/board/topic/1901-flux-control-panel-for-hercules/?p=14071

Warning: fopen(data/tmp/ConfigServers.cache.php) [function.fopen]: failed to open stream: Permission denied in /home/admin/www/cp/lib/Flux.php on line 275

In lib/Flux.php:

            if ($cache) {
                $fp = fopen($cachefile, 'w');
                fwrite($fp, '<?php exit("Forbidden."); ?>');
                fwrite($fp, $s=serialize($cf), strlen($s));
                fclose($fp);
            }

apparently the server is unable to write, and since the result of $fp isn't checked boom it screams php errors instead of one of these green flux error messages