Icon Field output empty

Hi!

I've create a block including the icon field. I'm using SVG codes (json file).
The dropdown works well and shows the icons and the icon titles.

The following code works well to get the icon title:

$icontitle = mb_get_block_field( 'icon' );
echo $icontitle;

I tried using the following code to display the icon but it doesn't output anything at all.

$icon = mb_the_block_field( 'icon' );
echo $icon;

How can I display the icon?