Undefined offset: 0 in metabox.php on line 309

Josh, you resolved the original bug report, but I suspect still you have a problem here.

1. Undefined offset: 0 in includes/metabox.php on line 309 error occur after front-end uploading under any circumstances
2. Setting “Add to Media Library” to unchecked produces an console error upon form submission “GET https://domain name/wp-content/uploads/2017/03/photo-30360.jpg 404 ()”
3. Alternatively, setting “Add to Media Library” to checked stores two copies of uploaded image in Media library (one marked as “Uploaded <Post title>”)

I use twenty seventeen theme, if this is important.

Thanks for your time. BR

ref: https://www.ads-software.com/support/topic/undefined-offset-0-in-metabox-php-on-line-309/#post-8899926