Question about TProfile error calculation

According to root.cern.ch/root/html/TProfile. … ildOptions,
the error of 0 spread bin should not be 0 unless Y=0 by default.
However, the following commands give me zero bin error:

TH2D *abc=new TH2D("xx","xx",10,0,10,10,-5,5) root [1] abc->Fill(4,3,0.1) (Int_t)113 root [2] ss=abc->ProfileX() (const class TProfile*)0x107ba470 root [3] ss->GetBinEntries(5) (const Double_t)1.00000000000000006e-01 root [4] ss->GetBinError(5) (const Double_t)0.00000000000000000e+00 root [5] ss->GetBinContent(5) (const Double_t)3.50000000000000000e+00
Is that a bug or not documented feature?