Improve defined/undefined/null handling in specific cases.

[Kevin Day]

Is your feature request related to a problem? Please describe.
While investigating #476, I found that there were a number of places that could have more precise checking.

I added those checks during the investigation but was able to solve the problem without them.
I removed those changes rather than having a more complicated hotfix in the PR.
This is a follow up to utilize the code (or something similar) that has a more aggressive or precise sanity checking in the area where I noticed the problem.

Describe the solution you'd like
Example solution:

• branch: https://github.com/TAMULib/SAGE/tree/478-improve_defined_undefined_null
• commit: b49d652

Describe alternatives you've considered
We could just leave the code alone as-is.
There are currently no observed problems.

[jcreel]

Our aim should be to document a local standard for treating the problematic behavior of bivalent logic in Javascript. Thanks to Kevin for getting the ball rolling.