#14448 Fix dangling formation names pointer in case data

RigCaseCellResultsData and RigFemPartResultsCollection held a raw pointer to RigFormationNames owned by a unique_ptr in RimFormationNames. Reloading or deleting the formation names left the case data with a dangling pointer. Store a copy instead, as RigFormationNames is a small value type with no identity.

ApplicationLibCode/ReservoirDataModel/RigFormationNames.cpp

@@ -27,6 +27,14 @@ RigFormationNames::RigFormationNames()
 {
 }
 
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+bool RigFormationNames::isEmpty() const
+{
+    return m_formationNames.empty();
+}
+
 //--------------------------------------------------------------------------------------------------
 ///
 //--------------------------------------------------------------------------------------------------