TMVA error

Hi
I was doing some BDT training using TMVA. When the training got completed I got this warning message. Can some one tell me what this warning means. I checked my input root files none of them has zero entries.Thank you.
Tools : histograms with zero entries: 569.282 : 0 cannot compute separation
— Tools : histograms with zero entries: 0 : 0 cannot compute separation

Anirvan

I’d like to bump this question up, please…

Eleni