Problem with combining characters

[jgm]

The following table

+-----------+-------+
| a         | back  |
+===========+=======+
| ø̞         | o̞     |
+-----------+-------+

gets parsed as having rowspans:

ArrayTable {arrayTableCells = array ((1,1),(2,2)) [((1,1),ContentCell 2 1 [" a         ","==========="," \248\798         "]),((1,2),ContentCell 2 1 [" back  ","======="," o\798     "]),((2,1),ContinuationCell (1,1)),((2,2),ContinuationCell (1,2))], arrayTableHead = Nothing, arrayTableFoot = Nothing, arrayTableColSpecs = array (1,2) [(1,(AlignDefault,11)),(2,(AlignDefault,7))]

Replacing the accented characters (formed with combining accents) with regular ascii letters makes the problem go away, so I assume it has to do with character width calculations.

Originally jgm/pandoc#9145.