Fix jokers

lib/day7.ex

@@ -6,8 +6,8 @@ defmodule Aoc2023.Day7 do
     |> Enum.frequencies()
     |> then(fn freq ->
       {jokers, freq_} = freq |> Map.pop(0, 0)
-      common = freq_ |> Enum.max_by(pipe(elem(1))) |> elem(0)
-      freq_ |> Map.update!(common, &(&1 + jokers))
+      common = freq_ |> Enum.max_by(pipe(elem(1)), fn -> {1, nil} end) |> elem(0)
+      freq_ |> Map.update(common, jokers, &(&1 + jokers))
     end)
     |> Enum.map(pipe(elem(1)))
     |> Enum.sort(:desc)