Empty bin

Dear all,

I am trying to plot my data,

RooPlot* frame = topMass->frame() ;
data->plotOn(frame) ;

starting from a dataset imported from a rootupla.
In the original ntupla some bins contains 0 entries, I mean they are empty.
But when I do plotOn(frame), the empty bins are filled with the entries 0.
And I do not want this.
I want to keep empty bins.

I have the same problem reported here some time ago (RooDataSet plots), so I tried with

but it does not work.

Could you please help me?