use initial ammo group form component select state

lib/cannery_web/live/ammo_group_live/form_component.ex

@@ -22,14 +22,23 @@ defmodule CanneryWeb.AmmoGroupLive.FormComponent do
 
   @spec update(Socket.t()) :: {:ok, Socket.t()}
   def update(%{assigns: %{current_user: current_user}} = socket) do
-    socket =
+    %{assigns: %{ammo_types: ammo_types, containers: containers}} = socket =
       socket
       |> assign(:ammo_group_create_limit, @ammo_group_create_limit)
-      |> assign_changeset(%{})
       |> assign(:ammo_types, Ammo.list_ammo_types(current_user))
       |> assign_new(:containers, fn -> Containers.list_containers(current_user) end)
 
-    {:ok, socket}
+    params =
+      if ammo_types |> List.first() |> is_nil(),
+        do: %{},
+        else: %{} |> Map.put("ammo_type_id", ammo_types |> List.first() |> Map.get(:id))
+
+    params =
+      if containers |> List.first() |> is_nil(),
+        do: params,
+        else: params |> Map.put("container_id", containers |> List.first() |> Map.get(:id))
+
+    {:ok, socket |> assign_changeset(params)}
   end
 
   @impl true