Scrub API's for null pointer checks

[skliper]

Is your feature request related to a problem? Please describe.
All pointers should be checked for NULL prior to accessing, a few cases where this was observed have been fixed but need to do a complete scrub.

Describe the solution you'd like
Scrub and add any missing null pointer checks

Describe alternatives you've considered
None

Additional context
Use the new macros...

Requester Info
Jacob Hageman - NASA/GSFC

[skliper]

Any other error checks (size != 0 or whatever) that make sense should also be added.