SUMMARY
***
With Marble versions 19.08 and 22.04.3, we are experiencing a seg fault when calling the iterator methods for GeoDataFolder. 

It looks like the d pointer is either becoming corrupted or is getting deleted, only for the iterator methods. I can call other methods without problems, such as at() and last(). I ran the same snippet with Marble 16.04 and it runs fine. 
***

STEPS TO REPRODUCE
1. Create an empty Qt+Marble project.
2. Add the following code to main:
    GeoDataFolder *myFolder = new GeoDataFolder();
    myFolder->begin();
3. Compile, build, and run the application.
4. Observe the crash.

OBSERVED RESULT
The application crashes due to a seg fault on the iterator begin command. 

I get a similar seg fault when I try to call end(). The stack trace shows the following:                                                                                        
                                                                                        
1 QVector<Marble::GeoDataFeature *>::isDetached qvector.h            113 0x7ffff78f0b36 
2 QVector<Marble::GeoDataFeature *>::detach     qvector.h            399 0x7ffff78f0cfa 
3 QVector<Marble::GeoDataFeature *>::begin      qvector.h            219 0x7ffff78ef4c9 
4 Marble::GeoDataContainer::begin               GeoDataContainer.cpp 349 0x7ffff78ee6fa 
5 main                                          main.cpp             54  0x55555555b6e4 


EXPECTED RESULT
The application should not crash when calling GeoDataFolder's begin/end methods.


SOFTWARE/OS VERSIONS
Windows: 10
macOS: 
Linux/KDE Plasma: Debian 10
(available in About System)
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version: 5.15.5

ADDITIONAL INFORMATION
This behavior has been observed on Debian. We have yet to test Windows.