fix for some segfault when running PVrefit

When enable ReFitPVs=True for FilterSelection in the Bs2JpsiPhi analysis where we had refit of tracks, particles and PV, I had the error below:

CheckRefittedPV...  ERROR FilterDesktop:: FilterDesktop::_save Element of saved decay tree not in TES. Likely memory leak! StatusCode=FAILURE
Bs2JpsiPhi_Sign...  ERROR Maximum number of errors ( 'ErrorMax':1) reached.
TupleSeq            ERROR Maximum number of errors ( 'ErrorMax':1) reached.
DaVinciUserSequ...  ERROR Maximum number of errors ( 'ErrorMax':1) reached.
DaVinciAnalysisSeq  ERROR Maximum number of errors ( 'ErrorMax':1) reached.
FilteredEventSeq    ERROR Maximum number of errors ( 'ErrorMax':1) reached.
DaVinciEventSeq     ERROR Maximum number of errors ( 'ErrorMax':1) reached.
EventLoopMgr      WARNING Execution of algorithm DaVinciEventSeq failed

The fix was provided by @ldufour long time ago.

To be tested with Rec!3347 (merged)