Undefined index: hreflang in metatag_hreflang_page_attachments_alter()

Notice: Undefined index: hreflang in metatag_hreflang_page_attachments_alter() (line 40 of metatag_hreflang.module)

This fixed the issue but i dont know how to write patches yet

if (strpos($element[1], 'hreflang_per_language') !== false) {
$hreflang_per_language[] = $element[0]['#attributes']['hreflang'];
}

to this :

if (strpos($element[1], 'hreflang_per_language') !== false && isset($element[0]['#attributes']['hreflang'])) {
$hreflang_per_language[] = $element[0]['#attributes']['hreflang'];
}