Fix geant4 settings in gconfig scripts

The scripts are the old way to define settings for geant3 and geant4 and are still used in some of the test macros. With this commit the changes already implemented in the new class CbmGeant4Settings some time ago with commits cb453d4b and 982c4b76 are added to fix errors during Geant4 initialisation.

These scripts are for example used in the macro/C2F/c2f_transport.C

sim/transport/gconfig/g4Config.C

@@ -61,11 +61,17 @@ void Config()
   if (cut == 0) gInterpreter->ProcessLine("SetCuts()");
 
 
-  //set geant4 specific stuff
+  // --- Random seed and maximum number of steps
+  size_t buf_size = 100;
+  Text_t buffer[buf_size];
   // Get the infomation about the seed value defined by SetSeed from the base class.
-  // Since ROOT 6.24 the derived classes return a differnt value.
-  Text_t buffer[50];
-  sprintf(buffer, "/random/setSeeds %i  %i ", gRandom->TRandom::GetSeed(), gRandom->TRandom::GetSeed());
+  // Since ROOT 6.24 the derrived classes return a differnt value.
+  Int_t randomSeed = gRandom->TRandom::GetSeed();
+  LOG(info) << "Set Geant4 random seed to " << randomSeed;
+  int result_length = snprintf(buffer, buf_size - 1, "/random/setSeeds %i  %i ", randomSeed, randomSeed);
+  if (!(result_length > 0 && result_length < static_cast<int>(buf_size))) {
+    LOG(fatal) << "Buffer overrun. Random seed for Geant4 would be improper.";
+  }
   geant4->ProcessGeantCommand(buffer);
 
   geant4->SetMaxNStep(10000);  // default is 30000