Fix: make sure point is finite before vicinity search

[nizar-sallem]

There is no test ensure that the point is valid before vicinity search.

[taketwo]

I think it's quite a common pattern to check if a cloud is dense and then have two branches, one with isFinite tests and the other without. Besides this test the code is often the same (i.e. copy-pasted). Perhaps we could introduce some sort of "finite point iterator" to iterate over a cloud. When the cloud is dense this is just a normal iterator, when the cloud is not dense, it incorporates the test. Will put this idea in my todo list.