Add check for NB_PROBES identifier and set default value

[rvandoosselaer]

fixes #1340

Check if the NB_PROBES identifier is set, if not set a default value of 0.

If needed I can remove the test class as I don't think it's really 'helpful' in this case, as it only loads and displays a model.

[stephengold]

The fix itself looks good.

Thank you for providing a test case. Please add an explanation of how to tell whether the test passed or failed.

[rvandoosselaer]

Hi, the only real check at the moment is looking at the log and see if a RenderException was thrown.

I don’t really see another way of checking this, unless you have an idea? If not, do you agree by keeping the fix and removing the test case?

[pspeed42]

Yeah, I think the test is "Does this PBR model crash on a Mac?" or not.

[pspeed42]

But maybe a comment in the test saying this would be good so someone doesn't have to look it up in github just to see. I think that might be what sgold is getting at.

[rvandoosselaer]

Ok that sounds like a good idea. I’ll adapt it and add some more context.

[stephengold]

I believe this PR is ready to be integrated.

[stephengold]

Integrated into the v3.3 branch at 9a84e72 .