Gets the part of the same table on the page before, when this table, detected from a page's geometry, continues one that ends
that page; null otherwise.
public LayoutTable? PreviousPart { get; }
ISO 32000-2 §14.8.4.8.3 (Table 371): a table broken across pages is one Table element. Detection reads each page on its
own, so the parts are separate tables linked here: a table that ends a page and one that starts the next with the same columns.
Tables of a structure tree are never split, and have no parts.