Fix air unit resupply #5966

OpenRA.Mods.Common/Activities/Air/FlyAttack.cs

@@ -41,7 +41,7 @@ namespace OpenRA.Mods.Common.Activities
 			// Move to the next activity only if all ammo pools are depleted and none reload automatically
 			// TODO: This should check whether there is ammo left that is actually suitable for the target
 			if (ammoPools.All(x => !x.Info.SelfReloads && !x.HasAmmo()))
-				return NextActivity;
+				return ActivityUtils.SequenceActivities(new ReturnToBase(self), NextActivity);
 
 			if (attackPlane != null)
 				attackPlane.DoAttack(self, target);