hmm.... not sure how that is possible, maybe it run twice?
Anyway, I guess if the issue is only that one editing the file install/upgrade_1-1.php changing:
'debug_title' => 'Converting gender data',
'function' => function ($db, $db_table)
{
$result = $db->query('', '
to:
'debug_title' => 'Converting gender data',
'function' => function ($db, $db_table)
{
return;
$result = $db->query('', '
this simply skips the step.
BTW, before doing that, try simply renaming the directory "install" to "install_bak" and see how the forum looks like.