number-rows-spanned should be non-negative integer

Hello

The "number-rows-spanned" and "number-columns-spanned" attributes of
fo:table-cell element should rather be non-negative integer than positivie
integer.
According to W3 the "0" is perfectly valid and moreover it has a special
meaning.

rows: The value zero ("0") means that the cell spans all rows from the
current row to the last row of the table section
(THEAD<http://www.w3.org/TR/html401/struct/tables.html#edef-THEAD>,
TBODY <http://www.w3.org/TR/html401/struct/tables.html#edef-TBODY>, or
TFOOT<http://www.w3.org/TR/html401/struct/tables.html#edef-TFOOT>)
in which the cell is defined.
columns: The value zero ("0") means that the cell spans all columns from the
current column to the last column of the column group
(COLGROUP<http://www.w3.org/TR/html401/struct/tables.html#edef-COLGROUP>)
in which the cell is defined.

XHTML:
http://www.w3.org/TR/xhtml2/mod-tables.html#adef_tables_rowspan
http://www.w3.org/TR/xhtml2/mod-tables.html#adef_tables_colspan

HTML:
http://www.w3.org/TR/html401/struct/tables.html#adef-rowspan
http://www.w3.org/TR/html401/struct/tables.html#adef-colspan

Best regards
  Jaroslav Záruba