Add support for null CIM instances

[ricmestre]

CIM instances can be null nevertheless DSCParser seems never had support for it so this PR tries to fix it.

[FabienTschanz]

I see, if I'm not mistaken this would fix a couple of issues over on the Microsoft365DSC repository.

[ricmestre]

There are 2 issues there, one I don't know if this fixes it or not since the OP didn't provide any configuration [0] but for the other actually won't solve it [1]

[0] microsoft/Microsoft365DSC#5737
[1] microsoft/Microsoft365DSC#5711

I actually came up with this fix because I had a customer with a genuine issue on your IntuneDeviceRemediation resource where the RunSchedule was being exported as null but ConvertTo-DscObject just barfs with that error "ConvertTo-DSCObject: Unable to find type [Instance]"

[FabienTschanz]

I see. I found another issue here: microsoft/Microsoft365DSC#5715. I colleague of mine reported this issue to me, but I didn't quite understand why it exported it as $null (although now, it makes sense to me). Thank you 👍

Edit: The issue with [1] should be fixed with microsoft/Microsoft365DSC#5746. The export is corrupted.

[ricmestre]

Yeah I saw your PR there and looks good to me.

But for #5715 would be good to see if that person could do an export from an older M365DSC version, this is because AADApplication was one of the resources where Nik refactored the CIM instances and I don't know if that's actually a genuine null instance like with my customer, or if it's an issue now exporting that resource.