[tmva][sofie] Fix ONNX fusion child indexing

nodesChildren is keyed by original graph node indices, while the parse
loop iterates over nodesOrder positions. Use nodesOrder[i] to retrieve
the correct child list for the currently parsed node and avoid incorrect
fusion pairing on reordered graphs.

Author: markknoffler

tmva/sofie_parsers/src/RModelParser_ONNX.cxx

@@ -873,7 +873,7 @@ void RModelParser_ONNX::ParseONNXGraph(RModel & rmodel, const onnx::GraphProto &
          std::cout << "\t" << i << "  " << nodesOrder[i] << " parsing operator " << op_type << std::endl;
       }
 
-      std::unique_ptr<ROperator> op = ParseOperator(i, graph, nodesOrder, nodesChildren[i]);
+      std::unique_ptr<ROperator> op = ParseOperator(i, graph, nodesOrder, nodesChildren[nodesOrder[i]]);
       if (!op) {
          if (verbose) {
             std::cout << "\t\tskipping operator since it is fused with previous one" << std::endl;