Added precompiler check for Geant4 version, as G4FindDataDir() doesn't exist in older ones

 * @throws ModuleError If a certain Geant4 dataset is not set or not available

 */

static void check_dataset_g4(const std::string& env_name) {

#if G4VERSION_NUMBER > 1100

    const char* file_name = G4FindDataDir(env_name.c_str());

#else

    const char* file_name = std::getenv(env_name.c_str());

#endif

    if(file_name == nullptr) {

        throw ModuleError("Geant4 environment variable " + env_name +

                          " is not set, make sure to source a Geant4 "