Fix logic for ignoring (col|row)span=1

1 should only be kept if the original value was 1 (previously
was just if the original value existed).

This means unmerging a cell doesn't result in (col|row)span=1.

Change-Id: I188755ccd435b21fa9791263aa84ccc89633cd0e
Merge "Fix logic for ignoring (col|row)span=1"