Add is null or empty

[sirknightj]

Issue #, if available:
N/A

Description of changes:

• Add a new macro to check for null string or empty string. For readability purposes,

if (!IS_NULL_OR_EMPTY(str)) {

is better than these two

if (!(str == NULL || str[0] == '\0')) {
if (str != NULL && str[0] != '\0') {

Other considerations

Why don't we just use strlen(str) > 0?

1. strlen has to traverse the entire string, so it's less efficient than a comparison with the null termination character.
2. If str is NULL, using strlen directly may result in undefined behavior.

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (83334d9) 75.12% compared to head (96dedbe) 75.12%.

❗ Current head 96dedbe differs from pull request most recent head 1514252. Consider uploading reports for the commit 1514252 to get more accurate results

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #228   +/-   ##
========================================
  Coverage    75.12%   75.12%           
========================================
  Files           52       52           
  Lines        10225    10225           
========================================
  Hits          7682     7682           
  Misses        2543     2543           

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