Account for tracks with nil length

lib/music_brainz/release.ex

@@ -22,7 +22,7 @@ defmodule MusicBrainz.Release do
   end
 
   def medium_duration(medium) do
-    Enum.sum_by(medium.tracks, fn track -> track.length end)
+    Enum.sum_by(medium.tracks, fn track -> track.length || 0 end)
   end
 
   def from_api_response(r) do

lib/music_library_web/live/collection_live/show.html.heex

@@ -316,7 +316,7 @@
               <span class="table-cell text-xs text-right pr-1">{track.position}</span>
               <span class="table-cell text-xs font-medium leading-8">{track.title}</span>
               <span class="table-cell text-xs text-right pl-2">
-                {format_duration(track.length)}
+                {track.length && format_duration(track.length)}
               </span>
             </div>
             <div :if={release_with_tracks.artists !== track.artists} class="table-row text-xs">