[gpad] Implement TRatioPlot::RecursiveRemove

TRatioPlot object was registered in list of cleanups,
but recursive remove was not implemented.
Therefore if any internal object was deleted before -
it make problem.

Fixes issue root-project#14855

graf2d/gpad/inc/TRatioPlot.h

@@ -173,6 +173,7 @@ class TRatioPlot : public TObject {
    void Draw(Option_t *chopt = "") override;
    void Browse(TBrowser *b) override;
 
+   void RecursiveRemove(TObject *obj) override;
 
    void Paint(Option_t *opt = "") override;
 

graf2d/gpad/src/TRatioPlot.cxx

@@ -108,7 +108,6 @@ TRatioPlot::TRatioPlot()
 
 TRatioPlot::~TRatioPlot()
 {
-
    gROOT->GetListOfCleanups()->Remove(this);
 
    auto safeDelete = [](TObject *obj) {
@@ -120,9 +119,8 @@ TRatioPlot::~TRatioPlot()
    safeDelete(fConfidenceInterval1);
    safeDelete(fConfidenceInterval2);
 
-   for (unsigned int i=0;i<fGridlines.size();++i) {
-      delete (fGridlines[i]);
-   }
+   for (auto &line : fGridlines)
+      safeDelete(line);
 
    safeDelete(fSharedXAxis);
    safeDelete(fUpperGXaxis);
@@ -138,6 +136,35 @@ TRatioPlot::~TRatioPlot()
    safeDelete(fLowYaxis);
 }
 
+////////////////////////////////////////////////////////////////////////////////
+/// Handle recursive remove of objects
+
+void TRatioPlot::RecursiveRemove(TObject *obj)
+{
+   if (!obj) return;
+
+   if (fRatioGraph == obj) fRatioGraph = nullptr;
+
+   if (fConfidenceInterval1 == obj) fConfidenceInterval1 = nullptr;
+   if (fConfidenceInterval1 == obj) fConfidenceInterval1 = nullptr;
+
+   for (auto &line : fGridlines)
+      if (line == obj) line = nullptr;
+
+   if (fSharedXAxis == obj) fSharedXAxis = nullptr;
+   if (fUpperGXaxis == obj) fUpperGXaxis = nullptr;
+   if (fLowerGXaxis == obj) fLowerGXaxis = nullptr;
+   if (fUpperGYaxis == obj) fUpperGYaxis = nullptr;
+   if (fLowerGYaxis == obj) fLowerGYaxis = nullptr;
+   if (fUpperGXaxisMirror == obj) fUpperGXaxisMirror = nullptr;
+   if (fLowerGXaxisMirror == obj) fLowerGXaxisMirror = nullptr;
+   if (fUpperGYaxisMirror == obj) fUpperGYaxisMirror = nullptr;
+   if (fLowerGYaxisMirror == obj) fLowerGYaxisMirror = nullptr;
+
+   if (fUpYaxis == obj) fUpYaxis = nullptr;
+   if (fLowYaxis == obj) fLowYaxis = nullptr;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 /// Internal method that shares constructor logic