*Created by: mhoemmen* @trilinos/tpetra @trilinos/teuchos @bartlettroscoe @ibaned Some Tpetra tests have been failing in debug mode. For example, FixedHashTable's test fails. `Teuchos::ArrayView`'s constructor that takes a pointer and a length throws, because the length is zero but the pointer is nonnull. When I stop `ArrayView`'s constructor from throwing, the test passes just fine. This is a bit of a problem, because `Kokkos::View` permits a View with a zero length to have a nonnull pointer. I can see the value of the test, but it is a bit troublesome to have to do an extra test to convert from `Kokkos::View` to `Teuchos::ArrayView`. Furthermore, `std::vector` behaves just like `Kokkos::View`, in that `.data()` need not return `nullptr` if the vector's length is zero. My plan was to go through Tpetra, find all instances of that constructor, and fix them. I plan to modify the relevant conversion functions in the TeuchosKokkosCompat subpackage, and only use those. However, it seems like this could lead to trouble when attempting obvious conversions from `std::vector` to `Teuchos::ArrayView`. Should we consider removing this debug test? See e.g., https://github.com/trilinos/Trilinos/issues/184 . ## Expectations Conversions from zero-length `std::vector` or `Kokkos::View` to `Teuchos::ArrayView` should not require an extra branch just to make the pointer null if the length is zero.