Add "null" as default value when using "php artisan translation:sync-missing-translation-keys"

[martinsjek]

I like using you package, but there is one slight thing that would fix a big issue for me.
When using "php artisan translation:sync-missing-translation-keys" the default "value" in database is set to empty string.
I would like to have it as NULL.
Why?
Because my Application will allow empty strings, but will hide the text if it's NULL.

Maybe there is a quick-fix on my end? If not maybe I could pass this as config parameter?