Revert "[treeplayer] prevent nullptr access in Restart (#19817)"

This reverts commit d95cff9.

Author: vepadulano

tree/treeplayer/src/TTreeReader.cxx

@@ -567,14 +567,9 @@ void TTreeReader::Restart()
    fProxiesSet = false; // we might get more value readers, meaning new proxies.
    fEntry = -1;
    if (const auto curFile = fTree->GetCurrentFile()) {
-      if (!fTree->GetTree()) {
-         fTree->LoadTree(0);
-      }
-      if (fTree->GetTree()) {
-         if (auto tc = fTree->GetTree()->GetReadCache(curFile, true)) {
-            tc->DropBranch("*", true);
-            tc->ResetCache();
-         }
+      if (auto tc = fTree->GetTree()->GetReadCache(curFile, true)) {
+         tc->DropBranch("*", true);
+         tc->ResetCache();
       }
    }
 }

tree/treeplayer/test/regressions.cxx

@@ -263,31 +263,3 @@ TEST(TTreeFormulaRegressions, WrongName)
       EXPECT_EQ(t.Draw("s.Eta()", ""), -1);
    }
 }
-
-// https://github.com/root-project/root/issues/19814
-TEST(TTreeReaderRegressions, UninitializedChain)
-{
-   auto filename = "eve19814.root";
-   auto treename = "events";
-   auto brname = "x";
-   const int refval = 19814;
-   {
-      TFile f(filename, "RECREATE");
-      TTree t(treename, "");
-      int x = refval;
-      t.Branch(brname, &x);
-      t.Fill();
-      f.Write();
-   }
-   {
-      TChain ch(treename);
-      ch.Add(filename);
-      TTreeReader reader(&ch);
-      reader.SetEntriesRange(0, ch.GetEntries());
-      EXPECT_EQ(reader.GetEntries(), 1);
-      TTreeReaderValue<int> x(reader, brname);
-      EXPECT_TRUE(reader.Next());
-      EXPECT_EQ(*x, refval);
-   }
-   gSystem->Unlink(filename);
-}