Add badge for tracks whose albums cannot be imported

Includes a small optimization that removes "" release IDs from the list
of IDs checked against releases in the database.

lib/music_library_web/live/stats_live/index.ex

@@ -20,10 +20,7 @@ defmodule MusicLibraryWeb.StatsLive.Index do
 
     recent_tracks = LastFm.Feed.all()
 
-    release_ids =
-      recent_tracks
-      |> Enum.map(fn t -> t.album.musicbrainz_id end)
-      |> Enum.uniq()
+    release_ids = release_ids(recent_tracks)
 
     collected_release_ids = Collection.collected_release_ids(release_ids)
     wishlisted_release_ids = Wishlist.wishlisted_release_ids(release_ids)
@@ -83,10 +80,7 @@ defmodule MusicLibraryWeb.StatsLive.Index do
   end
 
   def handle_info(%{tracks: recent_tracks}, socket) do
-    release_ids =
-      recent_tracks
-      |> Enum.map(fn t -> t.album.musicbrainz_id end)
-      |> Enum.uniq()
+    release_ids = release_ids(recent_tracks)
 
     collected_release_ids = Collection.collected_release_ids(release_ids)
     wishlisted_release_ids = Wishlist.wishlisted_release_ids(release_ids)
@@ -100,6 +94,13 @@ defmodule MusicLibraryWeb.StatsLive.Index do
      |> stream(:recent_tracks, recent_tracks, reset: true)}
   end
 
+  defp release_ids(recent_tracks) do
+    recent_tracks
+    |> Enum.map(fn t -> t.album.musicbrainz_id end)
+    |> Enum.uniq()
+    |> Enum.reject(fn musicbrainz_id -> musicbrainz_id == "" end)
+  end
+
   # The Tailwind build step requires all needed classes to be explicitly referenced
   # in the source code, and not dynamically generated. This implies that one cannot
   # (for example) interpolate a number in a class name.