pytest-icdiff causes hangs when terminal width is zero

I have found that in certain CI environments (CircleCI), terminal width is reported as zero, which seems to cause pytest-icdiff to hang (stops producing output and does not exit) when pytest finds an error. I don't have a compact reproducible example unfortunately (I can experiment with trying to make one), but hopefully it'll be helpful to have this report nonetheless (it took quite a while to sleuth out this much).

The problem occurs with pytest 7.1.3 and 7.2.0, under python 3.8.15 and python 3.9.10 (I haven't tested with other combinations). It occurs with pytest-icdiff 0.5 and 0.6.

The problem can be avoided by running `stty rows 50 cols 120` before starting pytest but one has to know to do that.