for image upload to work, the forms encoding type needs to be set to multipart/form-data
change the form tag:
<form action="tb_news_Update.php" method="post" name="WADAUpdateForm" id="WADAUpdateForm">
to:
<form action="tb_news_Update.php" method="post" enctype="multipart/form-data" name="WADAUpdateForm" id="WADAUpdateForm">