[NF] Fix lookup scope for inner names.

Belonging to [master]:
  - #2429
  - OpenModelica/OpenModelica-testsuite#943

Author: perost

Compiler/NFFrontEnd/NFLookup.mo

@@ -336,7 +336,7 @@ algorithm
     else
       // Continue looking in the instance parent's scope.
       prev_scope := cur_scope;
-      cur_scope := InstNode.parent(cur_scope);
+      cur_scope := InstNode.derivedParent(cur_scope);
     end try;
   end while;