Avoid possible divide by zero (#925)

Author: bramley

public_html/lists/admin/actions/processqueue.php

@@ -1323,7 +1323,7 @@ function sendEmailTest($messageid, $email)
          */
 
         $totaltime = $GLOBALS['processqueue_timer']->elapsed(1);
-        if ($counters['sent'] > 0) {
+        if ($counters['sent'] > 0 && $totaltime > 0) {
             $msgperhour = (3600 / $totaltime) * $counters['sent'];
             $secpermsg = $totaltime / $counters['sent'];
             $timeleft = ($counters['total_users_for_message '.$messageid] - $counters['sent']) * $secpermsg;