fix another error in aron dict if member is null

source/RobotAPI/libraries/aron/core/data/variant/container/Dict.cpp

@@ -112,7 +112,14 @@ namespace armarx::aron::data
         DictPtr ret(new Dict(p));
         for (const auto& [key, val] : getElements())
         {
-            ret->addElement(key, val->cloneAsVariant());
+            if (val)
+            {
+                ret->addElement(key, val->cloneAsVariant());
+            }
+            else
+            {
+                ret->addElement(key, nullptr);
+            }
         }
         return ret;
     }