fix(frontpage): attempt to fix crash
See #1220 (closed). This is not a certain fix, as we don't know for certain the cause of Unjournal's issue. But it appears likely that the cause is data of an unexpected type in at least one of their manuscripts, most likely in a CheckboxGroup or AuthorsInput field, or possibly a SupplementaryFiles or VisualAbstract field. An array is expected as the field's value, but it appears the value contains something else.