Fixes for malformed codes and valuesets

[JPercival]

• Fixes null pointer exceptions when codes are incompletely specified
• Fixes null pointer exceptions when valuesets are incompletely specified
• The above is accomplished by ignoring (i.e. filtering out) partially specified codes

[github-actions[bot]]

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[JPercival]

resolves #414

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (ba9bf60) 43.89% compared to head (a7f7121) 44.75%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #413 +/- ## ============================================ + Coverage 43.89% 44.75% +0.85% - Complexity 1663 1696 +33 ============================================ Files 224 224 Lines 11846 11851 +5 Branches 1658 1658 ============================================ + Hits 5200 5304 +104 + Misses 6026 5903 -123 - Partials 620 644 +24 ```

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