Fix some possible errors with the wooden rocket silo

lignumis/scripts/wooden-rocket-silo.lua

@@ -87,16 +87,17 @@ local function launch(event)
     if event.element.name ~= "provisional-rocket-silo-launch-button" then return end
     local player = game.get_player(event.player_index)
     local fake_silo = storage.rocket_silo_guis[player.index].fake_silo
+    if not fake_silo.valid then return end
     rocket_content = fake_silo.get_inventory(defines.inventory.chest).get_contents()
     for _, entry in pairs(storage.rocket_silos) do
-        if entry.fake_silo == fake_silo then
+        if entry.fake_silo == fake_silo and entry.real_silo.valid and entry.real_silo.rocket.valid then
             entry.player = event.player_index
             entry.rocket_content = rocket_content
             entry.cargo_pod = entry.real_silo.rocket.attached_cargo_pod
             fake_silo.destroy()
             entry.real_silo.launch_rocket()
             entry.cargo_pod.set_passenger(player)
-            break
+            return
         end
     end
 end