The url has ?id=38 instead of ?venue_id=38, so it doesn't match up with the code.
You can update the recordset to use id instead to make it match. Just update the line from:
$WADAvenue_update->bindParam("i", "".($_GET['venue_id']) ."", "-1"); //Paramvenue_id
$WADAvenue_update->bindParam("i", "".($_GET['id']) ."", "-1"); //Paramvenue_id
If this is a user update and not for administrators, then you shouldn't be using a $_GET variable that can be easily manipulated. You should be saving the id in the session when they log in and using a $_SESSION reference on the page so it can only be changed by logging into the correct user account.