Check document bodies contain mandatory fields, instead of just checking for emptiness.
- in one of the cases it was redundant to check for emptiness before checking the fields anyway
- checking for emptiness does not make sense, as there are a lot of 'errors' it does not catch in non-obvious ways: a) xmlns attributes count as non-emptiness b) unknown tags/attributes count as non-emptiness
Migrated from D4469 (view on Phabricator)