[tx] UFO glif parsing fails on contours with a single point

[punchcutter]

Parsing shouldn't just fail here. In this case the single points shouldn't be there, but tx could issue a warning and continue instead of failing with tx: (ufr) parsing failed and no other information.

[kaydeearts]

@hatchzo also added:

The zigzag/loop paths should be corrected by design and tx should report detailed information on parse errors. But I think the most serious problem is checkoutlineufo. It seems that those single point contours are generated while running checkoutlineufo. I made a test ufo file that only collect glyphs that cause errors and then run that : checkoutlinesufo -e -w -o test-check.ufo test.ufo

[punchcutter]

Dupe of https://github.com/adobe-type-tools/afdko/issues/1632 which has a good test that took me a while to track down where it was failing.