quotation fix; use double quotes with $ silly (thanks to ksb4ever - #2858717 )

git-svn-id: https://svn.code.sf.net/p/postfixadmin/code/trunk@719 a1433add-5e2c-0410-b055-b7f2511e0802

upgrade.php

@@ -600,7 +600,7 @@ function upgrade_4_pgsql() {
         COMMIT;"
     );
     if(!_pgsql_object_exists('mailbox_username_active')) {
-        db_query_parsed('CREATE INDEX mailbox_username_active ON $table_mailbox(username,active)');
+        db_query_parsed("CREATE INDEX mailbox_username_active ON $table_mailbox(username,active)");
     }