TypeError: in_array(): Argument #2 ($haystack) must be of type array, null given in in_array()

Created an MR!7 for fixing the type error in hook_migrate_prepare_row. please review.

#3 works well for me against 2.0.1-alpha6

@miwayha - it looks like the merge didn't work for some reason even though the MR has been approved; there's the error "An error occurred while merging. Try again." on the MR's page - https://git.drupalcode.org/project/disqus/-/merge_requests/7#note_364974

Could you retry please? This issue is affecting my sites too and it would be good for this fix to be in a release rather than needing to patch the module via Composer.

Thank you in advance :)

Alex