Fixing Geoloader leak probably introduced new bugs

[ChristianTackeGSI]

It looks like fixing the geoloader leak in #1444 introduced a new issue: https://cdash.gsi.de/testDetails.php?test=19713169&build=448354

I was not quickly able to track down what exactly is the problem here. But it seems to be related to FairGeoNodes probably being deleted and then used.

[dennisklein]

https://cdash.gsi.de/testDetails.php?test=19728299&build=448681 This shows also a segfault which is unrelated to your geoloader patches (v18.6_patches).

[dennisklein]

nvm, i confused the PR numbers...

[ChristianTackeGSI]

BTW, if we can't fix this for the 19.0 we should back out the geoloader stuff by

/// \bug Leaks GeoLoader and related resources, prevents memory issues (probably a double free)
///      See: https://github.com/FairRootGroup/FairRoot/issues/1514
(void)fGeoLoader.release();

in the FairRunSim dtor.

[ChristianTackeGSI]

For the time being #1518 has re-enabled the memory (including a proper marking). Still the problem of the unproper memory handling needs to be fixed.