Production upgrade path of the A8R7 assembly bugged

[ReDDoN45]

In a hands-off test campaign of the 44 campaign with computer production control, I´ve seen the Fw190A8/R7 assembly production upgrade to (), i.e. it upgrades to nothing, the assembly just vanishes for good.

I think this is easy to fix and related to the upgrade path of the Fw190A8/R7, as it is designed to upgrade to the Do-335B (at least this is stated in the tabula:

tm.asp?m=2376274

Since this aircraft is not directly produceable, as it is a gun-pack version of the Do-335A. Would be a good explaination for this self-destructory behaviour... Speer wouldn´t be happy either. Propably one should check through all those aircraft upgrades to be designated to upgrade to a gun-pack version of any plane and change it to the base version of the plane, as some players actually might use the computer production control.