Add 'document' as content type in case if it's defaulted due to plugin error

[elcreator]

is_scalar is not enough validation as it not checks for empty value.

Way to reproduce the original issue - insert table with i.e. 200 rows to the multiTv input, with 7 text inputs (columns) in multiTV and save.
It will not fail if you create 20 not 200 records it will save successfully, otherwise $content['type'] becomes empty and document loses Published status

[elcreator]

For everyone concerned about reality of this scenario and why it's should be fixed here and not only at MultiTV module/snippet level:
The way PHP limits extra fields (by default every field after first 1000) is just by removing them from $_POST array
https://www.php.net/manual/en/info.configuration.php#ini.max-input-vars
I.e. if snippet/plugin/module uses more than max-input-vars fields in the POST, this variable (and not only this one but also "published" etc) becomes empty.