fix(mechanics): Escorts stop following orders after the flagship dies (…

…endless-sky#10259)

source/AI.cpp

@@ -1550,9 +1550,12 @@ bool AI::FollowOrders(Ship &ship, Command &command) const
 
 	int type = it->second.type;
 
+	// Ships without an (alive) parent don't follow orders.
+	shared_ptr<Ship> parent = ship.GetParent();
+	if(!parent)
+		return false;
 	// If your parent is jumping or absent, that overrides your orders unless
 	// your orders are to hold position.
-	shared_ptr<Ship> parent = ship.GetParent();
 	if(parent && type != Orders::HOLD_POSITION && type != Orders::HOLD_ACTIVE && type != Orders::MOVE_TO)
 	{
 		if(parent->GetSystem() != ship.GetSystem())