no ATL-Tag in medium sized pictures

Hi,

I use the standard gallery function of WP, but the ALT attribute for images becomes not included in the HTML-Code.

here is a example, the alt-tag is available but empty.

Here is my code to show the picture in the image.php:

<p class=”attachment”>ID); ?>”><?php echo wp_get_attachment_image( $post->ID, ‘medium’ ); ?>

I’ve already changed the media.php with this code at line 330, but the alt-tag stays empty:

$html = ‘<img src=”‘.attribute_escape($src).'” alt=”‘.attribute_escape($alt).'” ‘.$hwstring.’class=”attachment-‘.attribute_escape($size).'” />’;

Please help me, this problem makes me crazy….