Error when expanding task-code ValueSet resource

[volodymyr-korzh]

Expanding task-code ValueSet after pre-expansion returns NullPointerException

To Reproduce

1. Start with a default implementation.
2. In Persistence module configuration and set the configurations to YES:

• Seed Base Validation Resources
• Lucene Indexing Enabled
• Enable Terminology Index

3. Save the updated configuration settings and restart the Persistence module.

4. Once the Persistence module has finished restarting (this may take several minutes), wait at least an additional 15 minutes to allow time for all ValueSet pre-expansions to complete.

5. Query that a ValueSet exists for http://hl7.org/fhir/ValueSet/task-code using a REST GET or browser e.g.:
   http://localhost:8000/ValueSet/?url=http://hl7.org/fhir/ValueSet/task-code

6. Request $expand operation on the same ValueSet using a REST GET or browser e.g.:
   http://localhost:8000/ValueSet/$expand/?url=http://hl7.org/fhir/ValueSet/task-code

Expected Behaviour:

Should return the expanded ValueSet.

Actual Behaviour:

Returns an OperationOutcome similar to:

{
  "resourceType": "OperationOutcome",
  "issue": [ {
    "severity": "error",
    "code": "processing",
    "diagnostics": "Failed to call access method: java.lang.NullPointerException"
  } ]
}