Hopsan FMUs crash if it contains subsystems

[robbr48]

Describe the bug
FMUs exported from Hopsan crashes if the exported model contains subsystems.

To Reproduce
If the bug can be reproduce, please give the steps taken to reproduce the behavior:

1. Create a Hopsan model with a subsystem
2. Export model to FMU
3. Import FMU to Hopsan (or other importing tool)
4. Simulate
5. Segmentation fault

Expected behavior
No segmentation fault :)

Hopsan version (please complete the following information):
Version information is shown in the message widget when HopsanGUI is started

• OS: Confirmed on both Windows 11 and Ubuntu
• Version: 2.21.0

[robbr48]

Problem seems to have disappeared, but let's keep this issue open just in case.