CodeSystem/$validate-code causes and NPE when display is not present in the data

[JohnTimm]

There are scenarios where a $validate-code operation causes a 500 Internal Server Error due to a NullPointerException on line 1042 of FHIRTermService. This is because, when the code system is case-sensitive, we must normalize the display name before we compare:

result = caseSensitive ? outcome.getDisplay().equals(coding.getDisplay()) : normalize(outcome.getDisplay().getValue()).equals(normalize(coding.getDisplay().getValue()));

We must add an additional null check on outcome.getDisplay.getValue() and coding.getDisplay().getValue() to protect against this.

[prb112]

QA - Tested for NPE, and found it returns properly