Fixed back-end warning infrastructure: The Print / PrintObject

should have been derived from ObjectBase, not from ObjectID.

src/libslic3r/SLAPrint.hpp

@@ -433,7 +433,7 @@ public:
     // in the notification center.
     const SLAPrintObject* get_object(ObjectID object_id) const {
         auto it = std::find_if(m_objects.begin(), m_objects.end(),
-            [object_id](const SLAPrintObject *obj) { return *static_cast<const ObjectID*>(obj) == object_id; });
+            [object_id](const SLAPrintObject *obj) { return obj->id() == object_id; });
         return (it == m_objects.end()) ? nullptr : *it;
     }