Extract apply_fallback_index to shared helper

Closes #92

lib/music_library_web/live/scrobbled_tracks_live/index.ex

@@ -232,7 +232,7 @@ defmodule MusicLibraryWeb.ScrobbledTracksLive.Index do
     track = ScrobbleActivity.get_track!(id)
 
     socket
-    |> apply_fallback_index(params)
+    |> apply_fallback_index(params, :tracks, &apply_action/3)
     |> assign(:page_title, gettext("Edit Track"))
     |> assign(:track, track)
     |> assign(:form, to_form(Track.changeset(track, %{})))
@@ -252,15 +252,6 @@ defmodule MusicLibraryWeb.ScrobbledTracksLive.Index do
     load_and_assign_tracks(socket, track_list_params)
   end
 
-  def apply_fallback_index(socket, params) do
-    if get_in(socket.assigns, [:streams, :tracks]) == nil do
-      socket
-      |> apply_action(:index, params)
-    else
-      socket
-    end
-  end
-
   @impl true
   def handle_info({MusicLibraryWeb.ScrobbledTracksLive.Form, {:saved, _track}}, socket) do
     {:noreply, load_and_assign_tracks(socket, socket.assigns.track_list_params)}