Empty input in settings crashes forum

[SKevo18]

If an input (e. g.: the-turk-diff.archiveLimit) is left blank, the forum encounters a boot error:

https://github.com/the-turk/flarum-diff/blob/7ff53a206b2727d1be34051f859cc9788dd56a8e/src/Jobs/ArchiveDiffs.php#L55-L55

Is it possible to mark the input as required in the admin frontend?