Undefined variable notice when update_post_meta()

[metodiew]

We are using this plugin for one of our client projects and I found an notice for undefined variable when update the post meta. I can't reproduce it right now while I'm testing it, but I'm 100% sure I saw this note in debug.log a few weeks ago.

I've asked about a GitHub repository here https://wordpress.org/support/topic/do-you-have-a-github-repository and I'll send a PR. Take a look and see if it's worth adding this check or not :)

[metodiew]

That's quite strange. Either my IDE (Eclipse) is playing with me or GitHub can't track the change.

It looks like the file spacing is a bit odd, at least here on my local installation, but here is the code:
before:

if (is_array($response)) {

        $shortlink = $response['data']['url'];

        update_post_meta($post_id, '_wpbitly', $shortlink);

    }

after:

if (is_array($response)) {
        if ( ! empty( $response['data']['url'] ) ) {
            $shortlink = $response['data']['url'];
            update_post_meta($post_id, '_wpbitly', $shortlink);
        }
    }

Sorry for the multiple comments :)