Fix UnsupportedOperationException

[jbonzohln]

Calling Engines.forRepository(repository) fails with an exception:

Caused by: java.lang.UnsupportedOperationException: null
    at java.base/java.util.AbstractList.add(AbstractList.java:155) ~[na:na]
    at java.base/java.util.AbstractList.add(AbstractList.java:113) ~[na:na]
    at org.opencds.cqf.fhir.cql.Engines.buildEnvironment(Engines.java:112) ~[cqf-fhir-cql-3.0.0.jar:3.0.0]
    at org.opencds.cqf.fhir.cql.Engines.forRepository(Engines.java:64) ~[cqf-fhir-cql-3.0.0.jar:3.0.0]
    at org.opencds.cqf.fhir.cql.Engines.forRepository(Engines.java:53) ~[cqf-fhir-cql-3.0.0.jar:3.0.0]
    at org.opencds.cqf.fhir.cql.Engines.forRepository(Engines.java:49) ~[cqf-fhir-cql-3.0.0.jar:3.0.0]
    at gov.ri.reporting.web.SampleController.<init>(SampleController.java:41) ~[classes/:na]
    at java.base/jdk.internal.reflect.DirectConstructorHandleAccessor.newInstance(DirectConstructorHandleAccessor.java:62) ~[na:na]
    at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:502) ~[na:na]
    at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:486) ~[na:na]
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:210) ~[spring-beans-6.1.3.jar:6.1.3]
    ... 21 common frames omitted

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 53.29%. Comparing base (44c3c06) to head (c38da4f).

Files	Patch %	Lines
...rc/main/java/org/opencds/cqf/fhir/cql/Engines.java	0.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #434 +/- ## ============================================ - Coverage 53.30% 53.29% -0.01% Complexity 2133 2133 ============================================ Files 281 281 Lines 11836 11837 +1 Branches 1618 1618 ============================================ Hits 6309 6309 - Misses 4912 4913 +1 Partials 615 615 ```

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