b478: possible bug by assign air groups on mission with 1/3 rule active

[catweasel]

I grouped 4 airplanes together, which landed again. After that, I assigned the whole group to an AAW patrol, selecting the 1/3 rule. Result: two of the planes in the group launched, while the remaining other two stay put on the airfield. Forming-up will thus never complete.

By the way, what I initally tried to achieve was an AAW patrol, where the launched fighters will form a group, instead being launched individually. To my knowledge, there is only the "micromanage" workaround available, i.e. either launch two of them as group and the assign them to the parol.