fix: add test coverage for api

lib/wanderer_app_web/controllers/common_api_controller.ex

@@ -91,7 +91,7 @@ defmodule WandererAppWeb.CommonAPIController do
     with {:ok, solar_system_str} <- APIUtils.require_param(params, "id"),
          {:ok, solar_system_id} <- APIUtils.parse_int(solar_system_str) do
       case CachedInfo.get_system_static_info(solar_system_id) do
-        {:ok, system} ->
+        {:ok, system} when not is_nil(system) ->
           # Get basic system data
           data = static_system_to_json(system)
 
@@ -105,6 +105,11 @@ defmodule WandererAppWeb.CommonAPIController do
           conn
           |> put_status(:not_found)
           |> json(%{error: "System not found"})
+
+        {:ok, nil} ->
+          conn
+          |> put_status(:not_found)
+          |> json(%{error: "System not found"})
       end
     else
       {:error, msg} ->