fix #29630 spatialindex for NaN points

[PeterPetrik]

fix #29630

[nyalldawson]

Won't we need a similar fix in QgsSpatialIndex also?

[PeterPetrik]

@nyalldawson fixed. crash with spatialindex can be reproduced by

1. load the test file from the issue
2. run in python console

l = iface.activeLayer()
i = QgsSpatialIndex(l)
f = l.getFeature(97)
i.deleteFeature(f)

[nyalldawson]

So now we just need some tests :)

[PeterPetrik]

@nyalldawson I tried to replicated the crash in the test system with both manually-prepared features as well as the layer from the issue without success. I can add some test with some random NaN numbers to the suite, but I am not sure how it represents the bug. The bug occurs only if the RTree is specifically filled with a set of NaN points and valid points with certain balancing. And also you need to remove specific fid from to tree to crash. Also you cannot replicate it on Linux at all (regardless of the version) so travis will not catch it anyways. Are you OK with not adding tests or should I add some test that just tests some random NaN points, but not the bug as such?

[nyalldawson]

Ok, that's fair enough!