bug with wpdb::insert

Assume I got an empty input like <input id=test" type="text" name="test">

Now get it with post and save it into a variable called data, and insert this data into the table, which looks like this:

$data = isset ( $_POST['test'] ) ? $_POST['test'] : 'empty';

if ( $data !== 'empty' ) {
   $new = sanitize_text_field ( $data );
   $wc_table_name = $wpdb -> prefix . 'my_table';
   $wpdb -> insert ( $wc_table_name, array ( 'name' => $new ) );
}

You would notice that it creates an empty row in the table if you submit the input with no value. The value is empty even without a space when I check it in the table of the database.