ST6RI-941 NPE when evaluating derived properties on feature chains

[AxelRICHARD]

Evaluating some SysML derived properties can fail with a NullPointerException when the model contains an unresolved feature chain.

The problem occurs in TypeUtil.getOwnedParametersOf(Type type). When the provided type is a Feature, the method first resolves its basic feature through FeatureUtil.getBasicFeatureOf(...). For a chained feature whose target has not been resolved yet, this call may return null. The method then unreferences that null value by calling
type.getOwnedFeature().

A concrete failing scenario is an AssignmentActionUsage containing an unresolved FeatureChaining. When its derived valueExpression property is evaluated, the computation asks TypeUtil
for owned parameters and triggers the NPE.

Expected behavior: unresolved feature chains should be treated as having no owned parameters at this stage, so derived property evaluation should return null or an empty result instead
of crashing.

This issue prevents robust handling of partially linked SysML models and can break workflows that evaluate derived properties before all feature chain references are resolved.