Improve defined/undefined/null handling in specific cases.

[kaladay]

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: https://github.com/TAMULib/SAGE/commit/b49d652b288d42edb92dff264befb4f10c148906

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.