UEF M2 - Fix issue if player builds air fac too quickly

[maudlin27]

If the player builds air fac before the objective to build it appears, then it remains even after the facility is captured, while if they build a transport subsequently it can cause an error message

[maudlin27]

For reference, the lua error message that prompted the change:
WARNING: Error running lua script: ...alliance\maps\scca_coop_e02\scca_coop_e02_script.lua(1204): attempt to call method `ManualResult' (a nil value)
stack traceback:
...alliance\maps\scca_coop_e02\scca_coop_e02_script.lua(1204): in function <...alliance\maps\scca_coop_e02\scca_coop_e02_script.lua:1202>