Check for de/allocations pointing to null

[vlkale]

Fix #256.

To address this problem showing up in LAMMPS, the allocate and deallocate functions of the Kokkos Tool library space time stack (which record and maintain in a C++ set the memory allocations in a Kokkos application) need to have a check for the case of two allocations being null. The comparison operator (<) cannot distinguish two elements in the set that are both null.

We need to have null pointer check of the parameter ptr, at the beginning of allocate and deallocate function. If the ptr variable null, then the function should simply return.

Within this null pointer check in space-time-stack allocation and deallocate functions, we should also discern whether the size of the ptr for allocation or deallocation is greater than 0 while the ptr is null. For that reason, we put in an assert just before returning.

[masterleinad]

You need to run clang-format.

[vlkale]

You need to run clang-format.

Thanks! Done.

[masterleinad]

Fine with me.