Fix NPE in EqConstList fixture reused by the store reloader test

[fh-ms]

Problem

The EqConstListData fixture (added in #304) asserts that the deserialized lists equalator survived serialization:

Assertions.assertInstanceOf(IntegerEquality.class, copy.getValue().equality(), "EqConstList equalator");

This passes in the serializer round-trip test (BasicSerializerTest), where the deserialized copy is fully populated. But the same fixture is reused by the store repos ReloaderSmokeTest.reloadTypeTest, which:

1. starts a storage with a freshly created (empty) fixture as root,
2. calls fillSampleData() without storing it,
3. reloadDeep(...) resets the root back to its stored empty state (value == null),
4. calls proveResults(...).

In that flow getValue() returns null, so the unconditional copy.getValue().equality() throws a NullPointerException, breaking the store integration tests (e.g. eclipse-store/store#764 CI, which builds against serializer main-SNAPSHOT).

Fix

Guard the equalator assertion on a populated list. It still runs in the serializer round-trip test (where the list is filled), but is skipped when the reloader resets the root to its stored empty state — matching the null-tolerant convention already used by the sibling EqBulkListData fixture.

Verification

BasicSerializerTest still passes (70 tests, 0 failures) with the equalator assertion exercised for the populated EqConstList, and the null-dereference that failed the store reloader test is eliminated.