Ref T579 Work around proximate cause of data race in CListModelBase.

This is still not thread-safe but at least it is less likely to crash.
A more robust fix will be attempted later.

src/blackgui/models/listmodelbase.cpp

@@ -545,10 +545,11 @@ namespace BlackGui
             }
 
             // sort the values
+            const auto tieBreakersCopy = m_sortTieBreakers; //! \todo workaround T579 still not thread-safe, but less likely to crash
             const std::integral_constant<bool, UseCompare> marker {};
             const auto p = [ = ](const ObjectType & a, const ObjectType & b) -> bool
             {
-                return Private::compareForModelSort<ObjectType>(a, b, order, propertyIndex, m_sortTieBreakers, marker);
+                return Private::compareForModelSort<ObjectType>(a, b, order, propertyIndex, tieBreakersCopy, marker);
             };
 
             return container.sorted(p);

src/blackgui/models/listmodelbasenontemplate.h

@@ -165,7 +165,7 @@ namespace BlackGui
 
             CColumns        m_columns;                         //!< columns metadata
             int             m_sortColumn;                      //!< currently sorted column
-            bool            m_modelDestroyed = false;          //!< model is about to be destroyed
+            bool            m_modelDestroyed = false;          //!< \todo rudimentary workaround for T579, can be removed
             Qt::SortOrder   m_sortOrder;                       //!< sort order (asc/desc)
             Qt::DropActions m_dropActions = Qt::IgnoreAction;  //!< drop actions
             BlackMisc::CPropertyIndexList m_sortTieBreakers;   //!< how column values are sorted if equal, if no value is given this is random