For image upload to function, the forms encoding type must be set to multipart/form-data
change the form tag:
<form action="products_Update.php?id=<?php echo(rawurlencode($row_WADAproducts['id'])); ?>" method="post" name="WADAUpdateForm" id="WADAUpdateForm">
to:
<form action="products_Update.php?id=<?php echo(rawurlencode($row_WADAproducts['id'])); ?>" method="post" enctype="multipart/form-data" name="WADAUpdateForm" id="WADAUpdateForm">