Notice: Undefined index for language in setTranslation()

A warning will show up for every field that is empty in the original node when trying to translate it, like this:

Notice: Undefined index: ar in EntityTranslationDefaultHandler->setTranslation() (line 662 of PATH/modules/contrib/entity_translation/includes/translation.handler.inc).

The actual code is checking if the field exists (it will), but if the field is empty, there will be no language code:

if ($field['translatable'] && isset($values[$field_name])) {
          $this->entity->{$field_name}[$langcode] = $values[$field_name][$langcode];
        }

The if sentence should check also if the language code exists:

if ($field['translatable'] && isset($values[$field_name][$langcode])) {

This doesn't seem to do any harm at all besides the warning.