Fix nil-index crash in move_record_in_set

lib/music_library/record_sets.ex

@@ -165,15 +165,18 @@ defmodule MusicLibrary.RecordSets do
       )
       |> Repo.all()
 
-    index = Enum.find_index(items, fn i -> i.record_id == record_id end)
+    case Enum.find_index(items, fn i -> i.record_id == record_id end) do
+      nil ->
+        :ok
 
+      index ->
         swap_index =
           case direction do
             :up -> index - 1
             :down -> index + 1
           end
 
-    if index && swap_index >= 0 && swap_index < length(items) do
+        if swap_index >= 0 and swap_index < length(items) do
           item_a = Enum.at(items, index)
           item_b = Enum.at(items, swap_index)
 
@@ -187,6 +190,7 @@ defmodule MusicLibrary.RecordSets do
             |> Repo.update!()
           end)
         end
+    end
 
     {:ok, get_record_set!(record_set.id)}
   end