How to ignore WP_ERROR caused by "get_the_excerpt" method in an AJAX call?

function get_post_data(){
    $post_id = $_POST['post_id'];
    ...
    $data['title'] = get_the_title( $post_id );
    ...
    $data['excerpt'] = get_the_excerpt( $post_id );        
    ...            
    echo json_encode( $data );

    wp_die();

}

The above code shows the scheme of the ajax call. Some data should be retriven from a post given by its ID outside the LOOP. This seems to work when the content fields like title and excerpt not empty. But when empty I get an Internal Server Error (500: admin-ajax.php not found). When I debug the PHP code it seems an WP_ERROR to be thrown after calling get_the_excerpt.

I just wanted to get some kind of solution like:

If (get_the_excerpt( $post_id ) returns an WP_ERROR) then let $data['excerpt'] = '';

Anything I tried f.e. try{} catch{} won't work, also not when I insert this to initialize the loop:

setup_postdata($post_id); 

in the second line of the get_post_data function.

(EDIT) RESOLVED:

The problem was caused by a conflict with the DIVI theme I used. When I followed the error in the WP_ERROR class I got:

Uncaught Error: Call to undefined function et_builder_init_global_settings() in [websitefolderpath]\wp-content\themes\Divi\includes\builder\feature\gutenberg\blocks\Layout.php:228

And this is getting relevant in the get_the_excerpt method in the following line:

return apply_filters( 'get_the_excerpt', $post-post_excerpt, $post );

After updating DIVI to the last version the error no longer exists.

Maybe I won't use get_the_excerpt() method in future in this project because it maybe can have many side effects causing strange results or errors.