在PHP脚本的IF中添加ELSE以获取默认Image

I have this code inserted in the Function.PHP file of my wordpress this. What it basically do is:

when ever the user clicks the pinterest button, it ignores all the images in the blog post page but instead choose/return the feature image to be pinned.

function catch_that_image( $size = 'full' ) {
    global $post;
    if ( has_post_thumbnail($post->ID) ) {
        $featured_image = wp_get_attachment_image_src( get_post_thumbnail_id($post->ID), $size);
        return $featured_image[0];
    }
    return false;
}

I have no problem with the code above, but then I realized that what if there's no featured image?

Is it possible if someone can modify the code for to to add the following IF and Else Condition:

IF Featured Image is Present:

Run the script above. (I think it's covered in the above code and works fine)

BUT IF THERE'S NOT FEATURED IMAGE, choose/return a default image to be pinned.

I'm not really sure how to integrate this code (below) to above code. Sorry but i lack of knowledge in this area.

if(empty($first_img)){ //Defines a default image
    $first_img = "http://www.mywebsite/wp-content/themes/Default_Image.jpg";
  }

THank you verymuch

Use the following code:

function catch_that_image( $size = 'full' ) {
   global $post;
   if ( has_post_thumbnail($post->ID) ) {
       $featured_image = wp_get_attachment_image_src( get_post_thumbnail_id($post->ID), $size);
       if(empty($featured_image[0])){ //Defines a default image
         $featured_image[0] = "http://www.mywebsite/wp-content/themes/Default_Image.jpg";
       }
       return $featured_image[0];
   }
   return false;
}