Fix cases where pilots were not returned.

https://github.com/dcs-liberation/dcs_liberation/issues/276

gen/flights/ai_flight_planner.py

@@ -257,6 +257,7 @@ class PackageBuilder:
         flights = list(self.package.flights)
         for flight in flights:
             self.global_inventory.return_from_flight(flight)
+            flight.clear_roster()
             self.package.remove_flight(flight)
 
 

gen/flights/flight.py

@@ -284,6 +284,9 @@ class Flight:
     def missing_pilots(self) -> int:
         return len([p for p in self.pilots if p is None])
 
+    def clear_roster(self) -> None:
+        self.squadron.return_pilots([p for p in self.pilots if p is not None])
+
     def __repr__(self):
         name = db.unit_type_name(self.unit_type)
         if self.custom_name: