Fix an uninitialised variable.

Found by coverity.

graf2d/graf/src/TCandle.cxx

@@ -56,6 +56,7 @@ TCandle::TCandle()
    fDismiss       = 0;
    fLogX          = 0;
    fLogY          = 0;
+   fLogZ          = 0;
    fNDrawPoints   = 0;
    fNHistoPoints  = 0;
    fAxisMin       = 0.;
@@ -87,6 +88,7 @@ TCandle::TCandle(const char *opt)
    fDismiss = 0;
    fLogX          = 0;
    fLogY          = 0;
+   fLogZ          = 0;
    fNDrawPoints   = 0;
    fNHistoPoints  = 0;
    fAxisMin       = 0.;
@@ -131,6 +133,7 @@ TCandle::TCandle(const Double_t candlePos, const Double_t candleWidth, Long64_t
    fOption        = kNoOption;
    fLogX          = 0;
    fLogY          = 0;
+   fLogZ          = 0;
    fNDrawPoints   = 0;
    fNHistoPoints  = 0;
    fAxisMin       = 0.;
@@ -164,6 +167,7 @@ TCandle::TCandle(const Double_t candlePos, const Double_t candleWidth, TH1D *pro
    fOption        = kNoOption;
    fLogX          = 0;
    fLogY          = 0;
+   fLogZ          = 0;
    fNDrawPoints   = 0;
    fNHistoPoints  = 0;
    fAxisMin       = 0.;