SSW does not prevent you from adding targeting computer to a mech with null-sig or void sig

[S2000Gan]

Describe the bug SSW allows you to add a targeting computer to a mech that has null-sig or void signature

To Reproduce Steps to reproduce the behavior:

1. Open/create a mech with null-sig or void-signature
2. Add a targeting computer

Expected behavior A mech with void-sig or null-sig is not allowed to mount a targeting computer, Note: When you try adding null-sig or void-sig to a mech with a targeting computer you get an error message preventing you from doing so, but not visa-versa.