Move initialization of $fDomain to viewlog.php

The other files using this variable (vacation.php and list-virtual.php)
initialize it properly.

variables.inc.php

@@ -20,7 +20,6 @@
  */
 
 $error = "";
-$fDomain = "";
 $fPassword = "";
 $fWhere = "";
 $tAlias = "";

viewlog.php

@@ -36,6 +36,7 @@ else {
    $list_domains = list_domains_for_admin ($SESSID_USERNAME);
 }
 
+$fDomain = '';
 if ($_SERVER['REQUEST_METHOD'] == "GET")
 {
    if ((is_array ($list_domains) and sizeof ($list_domains) > 0)) $fDomain = $list_domains[0];