A table whose range covers its header row alone makes Excel report the
workbook as unreadable; it repairs the file by dropping the table, so the
markup the table was written for is lost without a word.
Excel itself never writes such a table. Asked to make one over a single row
of headings, it writes the table over the row below as well and leaves that
row empty — its `sheetData` holds no cell for it, and the sheet dimension
stays at the headings. The writer now does the same, so what is written is
what Excel would have written.
The row below is taken only when it holds nothing. A table silently
swallowing a row that belongs to something else would change what the sheet
says, so that case throws instead, naming the row in the way.
Dmytro Kulyk