Adding fasteners breaks BOM generation

[nullbuilds]

Adding a fastener to an assembly and attempting to generate the BOM will result in the following error:

21:47:57  ASM4> BOM of the Assembly 4 Model
21:47:57  ASM4> BOM following sub-assemblies
21:47:57  Running the Python command 'Asm4_makeBOM' failed:
Traceback (most recent call last):
  File "C:\Users\Charl\AppData\Roaming\FreeCAD\Mod\Assembly4\.\makeBomCmd.py", line 116, in Activated
    self.listParts(self.model)
  File "C:\Users\Charl\AppData\Roaming\FreeCAD\Mod\Assembly4\.\makeBomCmd.py", line 451, in listParts
    self.listParts(subobj, level+1, parent=obj)
  File "C:\Users\Charl\AppData\Roaming\FreeCAD\Mod\Assembly4\.\makeBomCmd.py", line 381, in listParts
    x_count = obj.NumberX

'FeaturePython' object has no attribute 'NumberX'

It does not appear to matter whether the fastener has been attached to something or whether other parts exist in the file. While Assembly4's BOM command fails, the Generate BOM command of the Fasteners workbench does appear to be working correctly.

This was encountered with Assembly4 v0.50.4, Fasteners Workbench 0.4.70, and FreeCAD v0.21.1 (no other workbenches installed).

I've included a minimal example to reproduce the issue: BomTest.zip

[Zolko-123]

BoM is currently quite broken. If you have coding skills and time (and an itch to scratch) you are welcome to improve this