[1.18] Carriers with 0 size airgroup deployed in combat

[rimbecano]

If a carrier does not have an airgroup assigned, it will not be deployed in any battle. However, if it has an airgroup that is assigned, but not yet populated (basically, within the first turn after the airgroup is assigned), it will appear in battles.

Steps to reproduce:

1) Build a carrier.
2) During a war, add an airgroup.
3) Save.
4) Hit end turn.
5) After the interturn, exit without saving.
6) Repeat 4) and 5) until you get a battle with the carrier. It will have no aircraft aboard.

[williammiller]

Thanks for the report - posted to internal issue thread.