[RF] Address memory leaks in RooLagrangianMorphFunc
[RF] Address memory leaks in RooLagrangianMorphFunc

The `RooLagrangianMorphFunc` loads its input objects from a nested set of
`TFolders` stored in a `TFile`.  This MR adds protection (inspired by
[ROOT-9275](https://sft.its.cern.ch/jira/browse/ROOT-9275)) to avoid memory
leaks in the initialisation of the `RooLagrangianMorphFunc`, which for large
`RooFit` workspaces with many morphing functions can otherwise become
unfeasible to use.
olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root